Most view articles
2016, 45(2):282-286.
Abstract:
By improving the method of glass denucleating combined with cycle superheating based on traditional undercooling method, a stable undercooling above 200 K of 100g bulk K4169 is obtained, and the largest undercooling goes to 281 K. The effect of denucleating agent and superheating have been discussed. Moreover, the three-dimensional numerical analysis of temperature field inside the undercooled melt is presented, it can be found that the maximum temperature deviation in different parts is only 14K before nucleation. In contrast with the as-solidified microstructure, the grain size will increase with the increment of nucleating temperature. But the difference of microstructure is tiny and the average grain size is 12?2 μm.
By improving the method of glass denucleating combined with cycle superheating based on traditional undercooling method, a stable undercooling above 200 K of 100g bulk K4169 is obtained, and the largest undercooling goes to 281 K. The effect of denucleating agent and superheating have been discussed. Moreover, the three-dimensional numerical analysis of temperature field inside the undercooled melt is presented, it can be found that the maximum temperature deviation in different parts is only 14K before nucleation. In contrast with the as-solidified microstructure, the grain size will increase with the increment of nucleating temperature. But the difference of microstructure is tiny and the average grain size is 12?2 μm.
2 The formation and influence mechanism as well as experimental characterization of composite porosity
2016, 45(9):2282-2286.
Abstract:
In view of the common issue of composite porosity, the formation and influence mechanism of composite porosity are elucidated from the aspects of mechanical mixed nucleation theory and classic nucleation theory. The characterization of porosity morphology, distribution and size are conducted through specific test. The results show that: poor wettability of fibers, retention of vapor molecules and molecular volatilization generated during the crosslinking reaction are the main reasons of porosity formation. The lower cure pressures have a little effect on eliminating the porosity. With the increase of cure pressure, the porosity factor and porosity size decrease significantly. With the method of data fitting, the relations of porosity factor, porosity diameter and cure pressure are obtained, and the power function relations of three times are existed among them. This paper provides a theoretical and experimental support for optimizing the design of composites manufacturing process.
In view of the common issue of composite porosity, the formation and influence mechanism of composite porosity are elucidated from the aspects of mechanical mixed nucleation theory and classic nucleation theory. The characterization of porosity morphology, distribution and size are conducted through specific test. The results show that: poor wettability of fibers, retention of vapor molecules and molecular volatilization generated during the crosslinking reaction are the main reasons of porosity formation. The lower cure pressures have a little effect on eliminating the porosity. With the increase of cure pressure, the porosity factor and porosity size decrease significantly. With the method of data fitting, the relations of porosity factor, porosity diameter and cure pressure are obtained, and the power function relations of three times are existed among them. This paper provides a theoretical and experimental support for optimizing the design of composites manufacturing process.
2009, 38(3):515-518.
Abstract:
Au colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The effects of reductant amounts, mixing procedures, reaction time and stirring speed on the concentration, size, shape and monodispersity of Au colloid were investigated. UV-vis and TEM were used to characterize the size, shape, structure and optical properties of the samples. It's found that the optimal conditions for preparing Au colloid of small size are Na3C6H5O7(aq):HAuCl4(aq)=3:1(V:V), mixing Na3C6H5O7 firstly, reacting for 6 min and 650 r/min stirring speed. The colloid was prepared successfully which has superiority in shape, monodispersity and stability. The size of nanoparticles is only about 6~7 nm
Au colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The effects of reductant amounts, mixing procedures, reaction time and stirring speed on the concentration, size, shape and monodispersity of Au colloid were investigated. UV-vis and TEM were used to characterize the size, shape, structure and optical properties of the samples. It's found that the optimal conditions for preparing Au colloid of small size are Na3C6H5O7(aq):HAuCl4(aq)=3:1(V:V), mixing Na3C6H5O7 firstly, reacting for 6 min and 650 r/min stirring speed. The colloid was prepared successfully which has superiority in shape, monodispersity and stability. The size of nanoparticles is only about 6~7 nm
2010, 39(12):2169-2172.
Abstract:
High-quality freestanding GaN thick films were deposited by hydride vapor phase epitaxy (HVPE) on sapphire wafer with a thin Ti film on the top. The FWHM of (0002) peaks in the X-ray rocking curve profile is 260 arcsec. The FWHM of band edge emission peaks at 5 K and room temperature are 3 meV and 20 meV, respectively. The yellow spectral region is not observed at room temperature. The surface morphology of GaN films was characterized by scanning electron microscope; results show that hexagonal pits from dislocation extension exist on the surface of freestanding GaN thick films after corrosion and their dislocation density is estimated as 2.1×l07 cm-2. All these results prove that the Ti metal interlayer improves the crystalline quality of GaN epitaxial layer. The results of Raman and PL show that the surface stress of the GaN films is released completely. Finally, the temperature-dependent PL was investigated; the result also proves that the stress-free freestanding GaN thick films have high crystalline quality and optical quality
High-quality freestanding GaN thick films were deposited by hydride vapor phase epitaxy (HVPE) on sapphire wafer with a thin Ti film on the top. The FWHM of (0002) peaks in the X-ray rocking curve profile is 260 arcsec. The FWHM of band edge emission peaks at 5 K and room temperature are 3 meV and 20 meV, respectively. The yellow spectral region is not observed at room temperature. The surface morphology of GaN films was characterized by scanning electron microscope; results show that hexagonal pits from dislocation extension exist on the surface of freestanding GaN thick films after corrosion and their dislocation density is estimated as 2.1×l07 cm-2. All these results prove that the Ti metal interlayer improves the crystalline quality of GaN epitaxial layer. The results of Raman and PL show that the surface stress of the GaN films is released completely. Finally, the temperature-dependent PL was investigated; the result also proves that the stress-free freestanding GaN thick films have high crystalline quality and optical quality
5 Effects of Yttrium and Neodymium on Microstructure and Mechanical Properties of AZ81 Magnesium Alloy
2008, 37(1).
Abstract:
研究了复合添加稀土(Y,Nd)含量(1%～4%)对AZ81镁合金微观组织和力学性能的影响.结果表明,适量稀土元素的加入使AZ81镁合金的组织明显细化,β(Mg17Al12)相减少,同时析出了粒状的化合物Al2Y,Al2Nd.经固溶时效处理后,随着复合稀土含量的增加,在室温、150 ℃和250 ℃ 3个温度下,合金的强度和延伸率基本上呈先升后降的趋势.当稀土含量为2%时,合金的室温强度和150 ℃高温强度同时达到最大值,分别为282 MPa和212 MPa;在各温度下稀土含量为2%时延伸率最好.
研究了复合添加稀土(Y,Nd)含量(1%～4%)对AZ81镁合金微观组织和力学性能的影响.结果表明,适量稀土元素的加入使AZ81镁合金的组织明显细化,β(Mg17Al12)相减少,同时析出了粒状的化合物Al2Y,Al2Nd.经固溶时效处理后,随着复合稀土含量的增加,在室温、150 ℃和250 ℃ 3个温度下,合金的强度和延伸率基本上呈先升后降的趋势.当稀土含量为2%时,合金的室温强度和150 ℃高温强度同时达到最大值,分别为282 MPa和212 MPa;在各温度下稀土含量为2%时延伸率最好.
2009, 38(2):368-372.
Abstract:
Noble metal core-shell nanoparticles have attracted much attention due to their unique optical, electric and catalytic properties, they can be applied in material sciences, biophysics, molecular electronics and fluorescence-spectral engineering based on surface- enhancement. In this paper, a comprehensive review is presented on noble metal core-shell nanoparticles including preparation, application, and then the development trends of noble metal core-shell materials were also proposed
Noble metal core-shell nanoparticles have attracted much attention due to their unique optical, electric and catalytic properties, they can be applied in material sciences, biophysics, molecular electronics and fluorescence-spectral engineering based on surface- enhancement. In this paper, a comprehensive review is presented on noble metal core-shell nanoparticles including preparation, application, and then the development trends of noble metal core-shell materials were also proposed
2003(6):464-467.
Abstract:
Some new magnetic properties would be produced during processing for the stainless steel fibers. The magnetic parameters had been obtained through a systemic testing and microstructure observation by XRD for the stainless steel fibers. The results showed that the change of composing phases, the internal stress and the microstructure had insignificant effects on the magnetic properties for the stainless steel fibers. It was important to optimize the processing parameters and to expend the application fields for the stainless steel fibers.
Some new magnetic properties would be produced during processing for the stainless steel fibers. The magnetic parameters had been obtained through a systemic testing and microstructure observation by XRD for the stainless steel fibers. The results showed that the change of composing phases, the internal stress and the microstructure had insignificant effects on the magnetic properties for the stainless steel fibers. It was important to optimize the processing parameters and to expend the application fields for the stainless steel fibers.
8 Films
2002(1):73-75.
Abstract:
研究了射频反应溅射三元化合物CdIn2O4薄膜的电学和光学性质，讨论了反应气体中氧气浓度和热处理对CdIn2O4薄膜红外反射率的影响，实验结果表明，CdIn2O4薄膜在红外区域具有很高的反射率，是一种极好的红外反射膜。用它用为冰箱内保温膜和室内及冷库保温窗玻璃，效果十分明显，是一种极好的保温和节能膜。
研究了射频反应溅射三元化合物CdIn2O4薄膜的电学和光学性质，讨论了反应气体中氧气浓度和热处理对CdIn2O4薄膜红外反射率的影响，实验结果表明，CdIn2O4薄膜在红外区域具有很高的反射率，是一种极好的红外反射膜。用它用为冰箱内保温膜和室内及冷库保温窗玻璃，效果十分明显，是一种极好的保温和节能膜。
2008, 37(6):1008-1011.
Abstract:
采用提拉法生长出了四方晶系白钨矿结构的掺铒钨酸钇钠晶体[分子式为Er3 :NaY(WO4)2,简称Er:NYW].通过XRD分析得到晶体的晶胞参数a=b=0.5279nm,c=1.1285nm.讨论了Er:NYW晶体的生长工艺,得出晶体生长的最佳工艺参数为:拉速2mm/h,转速35r/min,冷却速率18℃/h,最佳的轴向温度梯度为液面上0.7～1℃/mm.测试了Er:NYW晶体的Raman光谱,讨论了晶体的振动归属.由吸收光谱和荧光光谱可知,在1540、978、801 nm附近的吸收峰较强、较宽,有利于用半导体激光二极管泵浦.
采用提拉法生长出了四方晶系白钨矿结构的掺铒钨酸钇钠晶体[分子式为Er3 :NaY(WO4)2,简称Er:NYW].通过XRD分析得到晶体的晶胞参数a=b=0.5279nm,c=1.1285nm.讨论了Er:NYW晶体的生长工艺,得出晶体生长的最佳工艺参数为:拉速2mm/h,转速35r/min,冷却速率18℃/h,最佳的轴向温度梯度为液面上0.7～1℃/mm.测试了Er:NYW晶体的Raman光谱,讨论了晶体的振动归属.由吸收光谱和荧光光谱可知,在1540、978、801 nm附近的吸收峰较强、较宽,有利于用半导体激光二极管泵浦.
2009, 38(2):259-262.
Abstract:
The microstructure of Ti-6Al-4V joints by laser beam welding with different welding parameters was studied, and the tensile properties were investigated. The microstructure of welding seam by laser beam welding consists mainly of α′ martensite phase as well as some α″ phase. By increasing the weld heat input，the distribution of martensite becomes more dispersive and glomerate due to the molten pool stiring, the welding stress and the burning loss of alloy elements. However, the welding parameters have no obviously effects on both the phase composition and the phase ratio. The tensile strength of joints is higher than basal metal when welded with reasonable parameters
The microstructure of Ti-6Al-4V joints by laser beam welding with different welding parameters was studied, and the tensile properties were investigated. The microstructure of welding seam by laser beam welding consists mainly of α′ martensite phase as well as some α″ phase. By increasing the weld heat input，the distribution of martensite becomes more dispersive and glomerate due to the molten pool stiring, the welding stress and the burning loss of alloy elements. However, the welding parameters have no obviously effects on both the phase composition and the phase ratio. The tensile strength of joints is higher than basal metal when welded with reasonable parameters
2009, 38(3):398-403.
Abstract:
The complexity and diversity of microstructural information involved in Ti alloys makes it rather difficult to quantitatively analyze properties or describe microstructural evolution behavior. Feasible and rigorous models capable of quantifying various microstructural data are rarely researched. Based on metallographical characteristics and mechanism of microstructure evolution, applying the stereology and quantitative Metallography rules, a preliminary system of models and methods for quantifying many important microstructural features of Ti alloys was developed. The work is an exploration for investigating the microstructure evolution and the relationship between microstructure and performance of Ti alloys. These microstructural features mainly include phase volume fraction, β grain size, thickness of Widmanst?tten α laths, colony size, and α phase information (size/orientation/aspect) in some microstructures. Six rules for manual-splitting α phase on image processing was presented. These models and methods are feasible, and explained with some examples
The complexity and diversity of microstructural information involved in Ti alloys makes it rather difficult to quantitatively analyze properties or describe microstructural evolution behavior. Feasible and rigorous models capable of quantifying various microstructural data are rarely researched. Based on metallographical characteristics and mechanism of microstructure evolution, applying the stereology and quantitative Metallography rules, a preliminary system of models and methods for quantifying many important microstructural features of Ti alloys was developed. The work is an exploration for investigating the microstructure evolution and the relationship between microstructure and performance of Ti alloys. These microstructural features mainly include phase volume fraction, β grain size, thickness of Widmanst?tten α laths, colony size, and α phase information (size/orientation/aspect) in some microstructures. Six rules for manual-splitting α phase on image processing was presented. These models and methods are feasible, and explained with some examples
2011, 40(6):1089-1092.
Abstract:
The VO2(A) thin films with the property of the thermochromic phase transition were prepared by vacuum evaporation deoxidization technology with the V2O5 powders (purity≥99.99%) as starting materials. The morphology of the VO2(A) thin films were studied, which were affected by the annealing temperature, and its effects on the optical properties and electrical properties were also studied. The results show that the stratiform characteristics are weakened until disappear and the peak-like particles appear and become large when the annealing temperature increases from 500 oC to 540 oC; however, the peak particles diminish firstly and then become large when the annealing temperature continues to increase, but the sizes of the particles become similar, about 50 nm. With the alteration of the morphology, the parameters of the phase transition, such as the critical temperature, the order of magnitude and the hysteresis loop width will change correspondingly. As the critical temperature decreases, the transmission of the thin films will decrease correspondingly, but only the transmission in the middle infrared during the phase transition changes correspondingly to the order of magnitude.
The VO2(A) thin films with the property of the thermochromic phase transition were prepared by vacuum evaporation deoxidization technology with the V2O5 powders (purity≥99.99%) as starting materials. The morphology of the VO2(A) thin films were studied, which were affected by the annealing temperature, and its effects on the optical properties and electrical properties were also studied. The results show that the stratiform characteristics are weakened until disappear and the peak-like particles appear and become large when the annealing temperature increases from 500 oC to 540 oC; however, the peak particles diminish firstly and then become large when the annealing temperature continues to increase, but the sizes of the particles become similar, about 50 nm. With the alteration of the morphology, the parameters of the phase transition, such as the critical temperature, the order of magnitude and the hysteresis loop width will change correspondingly. As the critical temperature decreases, the transmission of the thin films will decrease correspondingly, but only the transmission in the middle infrared during the phase transition changes correspondingly to the order of magnitude.
2006, 35(4):581-584.
Abstract:
Five ternary complexes have been synthesized from europium with aromatic carboxylic acid(p-methylbenzoic acid, methoxybenzoic acid, m-chlorobenzoic acid, benzoic acid, p-hydroxylbenzoic acid) and acrylamide; and also characterized by means of elemental analysis, thermal analysis, FT-IR spectra and UV spectra. Fluorescence spectra show five ternary complexes have nice luminescent properties, the sequence of ability that the aromatic carboxylic acids transfer light energy to europium ion is as follows: benzoic acid > p-methylbenzoic acid > methoxybenzoic acid > m-chlorobenzoic acid > p-hydroxylbenzoic acid. At the same time, the ternary europium complexes containing a reactive ligand acrylamide will possibly have potential application on the fabrication of bonding-type europium polymer luminescent materials.
Five ternary complexes have been synthesized from europium with aromatic carboxylic acid(p-methylbenzoic acid, methoxybenzoic acid, m-chlorobenzoic acid, benzoic acid, p-hydroxylbenzoic acid) and acrylamide; and also characterized by means of elemental analysis, thermal analysis, FT-IR spectra and UV spectra. Fluorescence spectra show five ternary complexes have nice luminescent properties, the sequence of ability that the aromatic carboxylic acids transfer light energy to europium ion is as follows: benzoic acid > p-methylbenzoic acid > methoxybenzoic acid > m-chlorobenzoic acid > p-hydroxylbenzoic acid. At the same time, the ternary europium complexes containing a reactive ligand acrylamide will possibly have potential application on the fabrication of bonding-type europium polymer luminescent materials.
2015, 44(6):1455-1458.
Abstract:
The composite TiAlCN films were deposited by vacuum arc ion plating on GCr15 rings at 175 oC. The properties of the films were characterized by SEM,?EPMA,?XRD,?adhesion?tester,?nano-hardness?tester and UMT-2 high temperature tribometer. The results indicate that the surface of the films is smooth and dense without any obvious pores. There are a certain number of droplets on the surface of films. The thickness of the films is about 2 μm. The fcc structure of TiN is found in the films. The grain size of the films is from 10 to 30 nm. With the addition of C element into the film, (Ti0.5,Al0.5)N peak in XRD patterns appears in width. After adding C into TiAlN, the adhesion of the films declines. However, the adhesion increases slightly along with the increase of the C content, but Al and Ti ratio does not change significantly. Besides, the hardness and elastic modulus increase first and then decreases, and the friction coefficient is always declined
The composite TiAlCN films were deposited by vacuum arc ion plating on GCr15 rings at 175 oC. The properties of the films were characterized by SEM,?EPMA,?XRD,?adhesion?tester,?nano-hardness?tester and UMT-2 high temperature tribometer. The results indicate that the surface of the films is smooth and dense without any obvious pores. There are a certain number of droplets on the surface of films. The thickness of the films is about 2 μm. The fcc structure of TiN is found in the films. The grain size of the films is from 10 to 30 nm. With the addition of C element into the film, (Ti0.5,Al0.5)N peak in XRD patterns appears in width. After adding C into TiAlN, the adhesion of the films declines. However, the adhesion increases slightly along with the increase of the C content, but Al and Ti ratio does not change significantly. Besides, the hardness and elastic modulus increase first and then decreases, and the friction coefficient is always declined
2009, 38(3):443-446.
Abstract:
The flexible ITO films were fabricated on PET substrate by Ion Beam Assisted Deposition(IBAD), and the effects of SiO2 buffer layer on the properties of ITO films were researched. The properties of ITO films were studied using X-ray diffraction (XRD), UV-VIS spectrometer, four-point probe and optical profiler. The results show that the SiO2 interlayer between ITO films and PET results in an increase of X-ray peak intensity of ITO film and a decrease of resistivity to 1.21×10-3 Ω·cm; in addition, the transmittance decreases to 85% and the surface is relatively smooth. The resistivity of the ITO films bent to some extent keeps some stability
The flexible ITO films were fabricated on PET substrate by Ion Beam Assisted Deposition(IBAD), and the effects of SiO2 buffer layer on the properties of ITO films were researched. The properties of ITO films were studied using X-ray diffraction (XRD), UV-VIS spectrometer, four-point probe and optical profiler. The results show that the SiO2 interlayer between ITO films and PET results in an increase of X-ray peak intensity of ITO film and a decrease of resistivity to 1.21×10-3 Ω·cm; in addition, the transmittance decreases to 85% and the surface is relatively smooth. The resistivity of the ITO films bent to some extent keeps some stability
2013, 42(6):1231-1235.
Abstract:
Al element was substituted for In in the (In2Te3)0.09 (SnTe)0.91 compound with the same molar fraction and (In2Te3)0.09 (SnTe)0.91 and (In1.9Al0.1Te3)0.09(SnTe)0.91 compounds were prepared by spark plasma sintering. The microstructure and the thermoelectric property of the compounds were investigated. Results show that although the Seebeck coefficient of the sample is almost unchanged after Al doping, the electrical conductivity increases to 1×105 W-1·m-1 at 321 K and to 2.3×105 W-1·m-1 at 705 K, being at least 2.4~3 times that of Al free (In2Te3)0.09(SnTe)0.91 compound, and the lattice thermal conductivity is significantly decreased. The highest ZT value of 0.4 is obtained at 693 K, which is approximately 2 times as large as that of the Al-free (In2Te3)0.09(SnTe)0.91 compound at the same temperature.
Al element was substituted for In in the (In2Te3)0.09 (SnTe)0.91 compound with the same molar fraction and (In2Te3)0.09 (SnTe)0.91 and (In1.9Al0.1Te3)0.09(SnTe)0.91 compounds were prepared by spark plasma sintering. The microstructure and the thermoelectric property of the compounds were investigated. Results show that although the Seebeck coefficient of the sample is almost unchanged after Al doping, the electrical conductivity increases to 1×105 W-1·m-1 at 321 K and to 2.3×105 W-1·m-1 at 705 K, being at least 2.4~3 times that of Al free (In2Te3)0.09(SnTe)0.91 compound, and the lattice thermal conductivity is significantly decreased. The highest ZT value of 0.4 is obtained at 693 K, which is approximately 2 times as large as that of the Al-free (In2Te3)0.09(SnTe)0.91 compound at the same temperature.
2009, 38(3):477-480.
Abstract:
The content and distributing of P in Electroless Nickel/Immersion Gold (ENIG) surface finishes effect the reliability of interface between solder joint and surface finishes. 289 I/Os lead-free Sn-3.0Ag-0.5Cu BGAs was assembled on the ENIG print circuit board by reflow soldering technology. The print circuit board was tested by random vibration. After random vibration test, the failure and not failure samples were studied by X-ray, SEM, and EDX et al. The failure mechanism was confirmed and the relation of failure and content and distributing of P in ENIG finishes was discussed. The failure and not failure samples after vibration test show similar microstructure at the interface of solder joint and surface finishes. The cross-sectioning of the affected area shows a “tooth decay” effect of corrosion of the nickel layer, and “mud cracks” in the topography on the surface. The enrichment of P on the surface accelerated the oxidation of Ni, and also reduced the mechanical intensity of interface. The oxidation of Ni and the enrichment of P on the surface result in the crack of solder/finish interface
The content and distributing of P in Electroless Nickel/Immersion Gold (ENIG) surface finishes effect the reliability of interface between solder joint and surface finishes. 289 I/Os lead-free Sn-3.0Ag-0.5Cu BGAs was assembled on the ENIG print circuit board by reflow soldering technology. The print circuit board was tested by random vibration. After random vibration test, the failure and not failure samples were studied by X-ray, SEM, and EDX et al. The failure mechanism was confirmed and the relation of failure and content and distributing of P in ENIG finishes was discussed. The failure and not failure samples after vibration test show similar microstructure at the interface of solder joint and surface finishes. The cross-sectioning of the affected area shows a “tooth decay” effect of corrosion of the nickel layer, and “mud cracks” in the topography on the surface. The enrichment of P on the surface accelerated the oxidation of Ni, and also reduced the mechanical intensity of interface. The oxidation of Ni and the enrichment of P on the surface result in the crack of solder/finish interface
2015, 44(5):1169-1172.
Abstract:
The isothermal oxidation behavior of packed aluminide coatings of Ni-Cr-W superalloy at 1100 oC was investigated. Results from scanning electron microscopy and X-ray diffraction indicate that the oxidation dynamics curve of packed aluminide coatings can be divided into two stages: initial rapidly stage and metaphase slowly stage. Oxides on packed aluminide coatings surface have a transformation process as following: crystal θ-A12O3→equalaxial α-A12O3→α-A12O3→particle α-A12O3→particle unite α-A12O3 during the whole oxidation. During the initial stage of oxidation, carbides can be able to holdback coating degeneration caused by interdiffusion between Ni element and Al element.
The isothermal oxidation behavior of packed aluminide coatings of Ni-Cr-W superalloy at 1100 oC was investigated. Results from scanning electron microscopy and X-ray diffraction indicate that the oxidation dynamics curve of packed aluminide coatings can be divided into two stages: initial rapidly stage and metaphase slowly stage. Oxides on packed aluminide coatings surface have a transformation process as following: crystal θ-A12O3→equalaxial α-A12O3→α-A12O3→particle α-A12O3→particle unite α-A12O3 during the whole oxidation. During the initial stage of oxidation, carbides can be able to holdback coating degeneration caused by interdiffusion between Ni element and Al element.
2008, 37(1):1-5.
Abstract:
采用弯曲和循环拉伸实验研究了新型Ti-3Zr-2Sn-3Mo-15Nb(TLM)钛合金的形状记忆和超弹性性能.探讨了变形温度、总应变和热处理等对TLM钛合金形状记忆和超弹性的影响规律.结果表明:新合金在热轧态和在α β两相区固溶处理后空冷比从β相区固溶处理后空冷条件下具有较高的形变恢复率,最大恢复应变可达1.8%.随着总变形应变增加,形变恢复率降低.从β相区固溶处理后空冷后TLM合金具有较好的超弹性,优于热轧态或时效处理后TLM合金的超弹性能.
采用弯曲和循环拉伸实验研究了新型Ti-3Zr-2Sn-3Mo-15Nb(TLM)钛合金的形状记忆和超弹性性能.探讨了变形温度、总应变和热处理等对TLM钛合金形状记忆和超弹性的影响规律.结果表明:新合金在热轧态和在α β两相区固溶处理后空冷比从β相区固溶处理后空冷条件下具有较高的形变恢复率,最大恢复应变可达1.8%.随着总变形应变增加,形变恢复率降低.从β相区固溶处理后空冷后TLM合金具有较好的超弹性,优于热轧态或时效处理后TLM合金的超弹性能.
2012, 41(1):169-172.
Abstract:
The monolithic foamed gold was synthesized by seed-mediated growth with polystyrene (PS) template and casting procedure and heat treatment. The results indicate that the PS could be coated by gold colloid with average grain size of 4.6 nm which was made in toluene by the electrostatic effect. The deposited gold with thickness of 70-90 nm and grain size of 30-60 nm were obtained by electroless plating. It can be self-supported after the template removing. The casting procedure is analogous to slip-casting of ceramic that results in randomly-packed PS/Au spheres with void spaces between individual particles. The columniform foamed gold with hollow spheres of 8-9 μm, diameter of 4 mm, density of 1.5 g/cm3, and porosity of 92% was obtained after heat treatment.
The monolithic foamed gold was synthesized by seed-mediated growth with polystyrene (PS) template and casting procedure and heat treatment. The results indicate that the PS could be coated by gold colloid with average grain size of 4.6 nm which was made in toluene by the electrostatic effect. The deposited gold with thickness of 70-90 nm and grain size of 30-60 nm were obtained by electroless plating. It can be self-supported after the template removing. The casting procedure is analogous to slip-casting of ceramic that results in randomly-packed PS/Au spheres with void spaces between individual particles. The columniform foamed gold with hollow spheres of 8-9 μm, diameter of 4 mm, density of 1.5 g/cm3, and porosity of 92% was obtained after heat treatment.
2009, 38(2):327-330.
Abstract:
Using sodium hypophosphite as the reducing agent, polyvinyl pyrrolidone as the protecting agent, the nanosized silver powder was synthesized by chemical reduction method in a highly concentrated silver nitrate solution. Using the orthogonal design method of three factors and three levels, the optimal conditions to prepare the nanosized silver powder were obtained by studying the effects of following factors, such as the concentration of reducing agent, the doses of protecting agent and the temperature, on the particles size and morphology of silver powder. The pure nanosized silver powders with qusai-spherical shapes and homogeneous distribution and diameter of 30 nm to 50 nm were synthesized under the conditions of AgNO3 concentration of 1.0 mol/L, NaH2PO2·H2O concentration of 0.1 mol/L, PVP/AgNO3 weight ratio of 1∶1, pH=1~2 and at 40 ℃
Using sodium hypophosphite as the reducing agent, polyvinyl pyrrolidone as the protecting agent, the nanosized silver powder was synthesized by chemical reduction method in a highly concentrated silver nitrate solution. Using the orthogonal design method of three factors and three levels, the optimal conditions to prepare the nanosized silver powder were obtained by studying the effects of following factors, such as the concentration of reducing agent, the doses of protecting agent and the temperature, on the particles size and morphology of silver powder. The pure nanosized silver powders with qusai-spherical shapes and homogeneous distribution and diameter of 30 nm to 50 nm were synthesized under the conditions of AgNO3 concentration of 1.0 mol/L, NaH2PO2·H2O concentration of 0.1 mol/L, PVP/AgNO3 weight ratio of 1∶1, pH=1~2 and at 40 ℃
2011, 40(7):1188-1191.
Abstract:
It is one of the basic processes that the oxide film form and rupture in the tip of stress corrosion cracking (SCC) of nickel-base alloys in high temperature water environment of the nuclear pressure vessel. Because of the particularity of the propagating mode and morphology of the tip of SCC, the stress and strain in the tip of SCC constituted of the tip oxide film and base metal was simulated and analyzed under the micro scale based on the sub-model technology in ABAQUS software. The results show that the groove-type crack significantly affects the stress and the plastic strain in the oxide film at the SCC crack tip, and the longer the groove-type crack is, the more obvious the effect is. On the other hand, compared with stress, the plastic strain is more sensitive to the morphology of the tip of SCC; therefore, the plastic strain should be an appropriate mechanical parameter to investigate the oxide film character in the SCC crack tip
It is one of the basic processes that the oxide film form and rupture in the tip of stress corrosion cracking (SCC) of nickel-base alloys in high temperature water environment of the nuclear pressure vessel. Because of the particularity of the propagating mode and morphology of the tip of SCC, the stress and strain in the tip of SCC constituted of the tip oxide film and base metal was simulated and analyzed under the micro scale based on the sub-model technology in ABAQUS software. The results show that the groove-type crack significantly affects the stress and the plastic strain in the oxide film at the SCC crack tip, and the longer the groove-type crack is, the more obvious the effect is. On the other hand, compared with stress, the plastic strain is more sensitive to the morphology of the tip of SCC; therefore, the plastic strain should be an appropriate mechanical parameter to investigate the oxide film character in the SCC crack tip
2009, 38(3):496-499.
Abstract:
A new technology for preparation of TaC coating on Carbon/carbon composites is reported. TaC was turned from TaO2F·rH2O·TaF5, which was characterized by FITR, XRD and SEM. The morphologies of TaC coating at different temperatures were observed by SEM. At 1200 ℃, the TaC coating shows the particular form. When the heat treatment temperature increased to 1800 ℃, the TaC coating was mainly columnar. The formation mechanism of TaC is that Carbon atom diffuse into Ta2O5 deposit, which is coming from TaO2F·rH2O·TaF5 and reacted into TaC at high temperature. The morphology of TaC coating can be interpreted by the theory of Ta2O5 deposited nucleation
A new technology for preparation of TaC coating on Carbon/carbon composites is reported. TaC was turned from TaO2F·rH2O·TaF5, which was characterized by FITR, XRD and SEM. The morphologies of TaC coating at different temperatures were observed by SEM. At 1200 ℃, the TaC coating shows the particular form. When the heat treatment temperature increased to 1800 ℃, the TaC coating was mainly columnar. The formation mechanism of TaC is that Carbon atom diffuse into Ta2O5 deposit, which is coming from TaO2F·rH2O·TaF5 and reacted into TaC at high temperature. The morphology of TaC coating can be interpreted by the theory of Ta2O5 deposited nucleation
2016, 45(9):2201-2207.
Abstract:
In this study, the microstructure, phase assemblages, hardness and wear properties of Al0.5CoCrCuFeNiBx (x=0-1) high-entropy alloys were investigated. The parameters representing simple solid-solution formation ability in Al0.5CoCrCuFeNiBx alloys were estimated. Without boron addition, the alloy was composed of simple FCC solid solution structure. With the addition of boron, the alloys were composed of borides and simple FCC solid solution matrix phase. Boron precipitated as borides instead of entering the crystal structure and thus there is no change in the lattice constant of the matrix FCC phase. Borides precipitation significantly hardens the alloy and the hardness showed a strong correlation to the boron content. There was no distinct difference in the wear resistance of the alloys with x?0.4, but the wear resistance showed a strong relation to the boron content in the alloys with x?0.6. With increasing boron content, the wear mechanism changes from delamination wear to oxidative wear. The great enhancement in the hardness and wear resistance is attributed to the combination of the large hard borides and relatively ductile and tough FCC matrix.
In this study, the microstructure, phase assemblages, hardness and wear properties of Al0.5CoCrCuFeNiBx (x=0-1) high-entropy alloys were investigated. The parameters representing simple solid-solution formation ability in Al0.5CoCrCuFeNiBx alloys were estimated. Without boron addition, the alloy was composed of simple FCC solid solution structure. With the addition of boron, the alloys were composed of borides and simple FCC solid solution matrix phase. Boron precipitated as borides instead of entering the crystal structure and thus there is no change in the lattice constant of the matrix FCC phase. Borides precipitation significantly hardens the alloy and the hardness showed a strong correlation to the boron content. There was no distinct difference in the wear resistance of the alloys with x?0.4, but the wear resistance showed a strong relation to the boron content in the alloys with x?0.6. With increasing boron content, the wear mechanism changes from delamination wear to oxidative wear. The great enhancement in the hardness and wear resistance is attributed to the combination of the large hard borides and relatively ductile and tough FCC matrix.
2009, 38(2):255-258.
Abstract:
Microstructure and formation characteristic of laser welded lap joints of TC4 alloy were investigated, and a parameter named join rate ψ was introduced to evaluate the welding effect of lap welding. The results indicated: the width of weld bead increases with increasing laser power or decreasing welding velocity, the top width of weld bead is larger than the bottom width and the minimum is the middle layer. And the join rate decreases as plates space or energy input increases. Microstructure of weld bead consisted of α′ martensite, and the martensite in the top portion is more concentrate than that in the bottom portion. There ate a small amount of martensite in HAZ, and distributed in gradient. For the strengthen effect of martensite, the microhardness reduces from the center of joints to base metal in cross direction, and the microhardness is higher in top weld bead
Microstructure and formation characteristic of laser welded lap joints of TC4 alloy were investigated, and a parameter named join rate ψ was introduced to evaluate the welding effect of lap welding. The results indicated: the width of weld bead increases with increasing laser power or decreasing welding velocity, the top width of weld bead is larger than the bottom width and the minimum is the middle layer. And the join rate decreases as plates space or energy input increases. Microstructure of weld bead consisted of α′ martensite, and the martensite in the top portion is more concentrate than that in the bottom portion. There ate a small amount of martensite in HAZ, and distributed in gradient. For the strengthen effect of martensite, the microhardness reduces from the center of joints to base metal in cross direction, and the microhardness is higher in top weld bead
2010, 39(2):243-248.
Abstract:
The effects of 3%-5% rhenium addition (mass fraction, similarly hereinafter) on the high-temperature corrosion resistance of CoNiCrAlY alloys were evaluated at 1000 ℃ by means of XRD, SEM and EDS. It is shown that there is an internal oxidation whether the rhenium is added to the alloy or not. The addition of rhenium can reduce the thickness of Al-depletion zone, stabilize the α-Cr(Re) phase and benefit the formation of Cr2O3 oxide scale which separates the base material from the molten salt and prevents from high-temperature corrosion
The effects of 3%-5% rhenium addition (mass fraction, similarly hereinafter) on the high-temperature corrosion resistance of CoNiCrAlY alloys were evaluated at 1000 ℃ by means of XRD, SEM and EDS. It is shown that there is an internal oxidation whether the rhenium is added to the alloy or not. The addition of rhenium can reduce the thickness of Al-depletion zone, stabilize the α-Cr(Re) phase and benefit the formation of Cr2O3 oxide scale which separates the base material from the molten salt and prevents from high-temperature corrosion
2010, 39(2):189-193.
Abstract:
Physical properties of Ni46Mn35Ga19 single crystal with transition temperatures above room temperature were investigated by various measuring methods. The measuring results of the resistance and ac susceptibility indicate that the magnetic transition and martensitic transformation can occur simultaneously in this alloy. The measurements of the isothermal magnetization show that the increasing rate of magnetic entropy change in this alloy is 9.0 J / kg·K·T. A large magnetic entropy change of 13.8 J/kg·K is obtained under the field of 1.6 T in the single crystal. Furthermore, the strain measurement shows that accompanying with magnetic entropy change, the alloy exhibits a large spontaneous transition strain of –0.89% and a large magnetic-field-enhanced strain of –1.90%.
Physical properties of Ni46Mn35Ga19 single crystal with transition temperatures above room temperature were investigated by various measuring methods. The measuring results of the resistance and ac susceptibility indicate that the magnetic transition and martensitic transformation can occur simultaneously in this alloy. The measurements of the isothermal magnetization show that the increasing rate of magnetic entropy change in this alloy is 9.0 J / kg·K·T. A large magnetic entropy change of 13.8 J/kg·K is obtained under the field of 1.6 T in the single crystal. Furthermore, the strain measurement shows that accompanying with magnetic entropy change, the alloy exhibits a large spontaneous transition strain of –0.89% and a large magnetic-field-enhanced strain of –1.90%.
2009, 38(3):532-535.
Abstract:
Using simple and efficient template method, sphere assembled structure; shuttle-like structure and flake assembled structure of calcium carbonate were obtained. The morphologies of products were researched, and the sphere assembled calcium carbonate with large surface was modified and combined with silver nanoparticles to obtain the silver nanoparticle/calcium carbonate composite for the first time. The composite has extensive applications in sterilization and medicine areas etc. The composite can not only reduce the silver quantity, but also provide a good route for applications of calcium carbonate nanomaterials
Using simple and efficient template method, sphere assembled structure; shuttle-like structure and flake assembled structure of calcium carbonate were obtained. The morphologies of products were researched, and the sphere assembled calcium carbonate with large surface was modified and combined with silver nanoparticles to obtain the silver nanoparticle/calcium carbonate composite for the first time. The composite has extensive applications in sterilization and medicine areas etc. The composite can not only reduce the silver quantity, but also provide a good route for applications of calcium carbonate nanomaterials
2009, 38(2):373-376.
Abstract:
Introduce the application area of rhenium including petrochemical, aeronautics and astronautics, metallurgy and electron industry and others. Systemic summarize and analyzed the main preparation methods of rhenium products, point out various preparation methods of rhenium and rhenium alloys
Introduce the application area of rhenium including petrochemical, aeronautics and astronautics, metallurgy and electron industry and others. Systemic summarize and analyzed the main preparation methods of rhenium products, point out various preparation methods of rhenium and rhenium alloys
2009, 38(3):559-564.
Abstract:
In this paper, the fabrication methods of magnesium matrix composites were introduced and the new fabrication process was emphasized. The effects of the fabrication processes on the composition, structure and properties of the composites were analyzed. Developing new reinforcements and novel in-situ reaction synthesis, optimizing the fabrication process and preparing high performance composites on larger scale are main research keys to the magnesium matrix composites
In this paper, the fabrication methods of magnesium matrix composites were introduced and the new fabrication process was emphasized. The effects of the fabrication processes on the composition, structure and properties of the composites were analyzed. Developing new reinforcements and novel in-situ reaction synthesis, optimizing the fabrication process and preparing high performance composites on larger scale are main research keys to the magnesium matrix composites
2009, 38(10):1769-1773.
Abstract:
Hypereutectic Al-20Si (mass fraction) alloy hollow tubes were prepared by centrifugal casting under an electromagnetic field (EMF). Effects of EMF on the solidification microstructure of the alloy and morphology of primary Si phases were investigated. Results show that primary Si phases in the solidification microstructure were refined after applying EMF compared with the microstructure of the Al-20Si hypereutectic alloys by conventional centrifugal casting. The segregation layer width of Si phases in the outer of the tube decreased gradually with the increase of the EMF intensity. The morphology of the Si phases in the outer of the tube changed from typical pentagram into dendrites grown along the heat flow direction. The phenomena of dulling and congregation of the Si phases in the inner of the tube were found due to EMF stirring. The size and aspect ratio of the primary Si phase decreased little by little with the increase of EMF intensity. The electromagnetic stirring destroyed the radial configuration of Si phases, eutectic Si phases distributed randomly, and the eutectic lamina spaces in the eutectic cell increased gradually.
Hypereutectic Al-20Si (mass fraction) alloy hollow tubes were prepared by centrifugal casting under an electromagnetic field (EMF). Effects of EMF on the solidification microstructure of the alloy and morphology of primary Si phases were investigated. Results show that primary Si phases in the solidification microstructure were refined after applying EMF compared with the microstructure of the Al-20Si hypereutectic alloys by conventional centrifugal casting. The segregation layer width of Si phases in the outer of the tube decreased gradually with the increase of the EMF intensity. The morphology of the Si phases in the outer of the tube changed from typical pentagram into dendrites grown along the heat flow direction. The phenomena of dulling and congregation of the Si phases in the inner of the tube were found due to EMF stirring. The size and aspect ratio of the primary Si phase decreased little by little with the increase of EMF intensity. The electromagnetic stirring destroyed the radial configuration of Si phases, eutectic Si phases distributed randomly, and the eutectic lamina spaces in the eutectic cell increased gradually.
2009, 38(4):691-695.
Abstract:
The V2O5 thin film was prepared on the substrates of Si glass and commercial glass by the sol-gel technique. The samples prepared were annealed in air atmosphere at different temperatures. The microstructure, the morphology and optical properties of V2O5 thin films were studied by XRD, SEM and spectrophotometer. The results of XRD and SEM indicate that the better crystalline states and orientation with V2O5 (001) and (200) after annealing can be obtained, and the grain homogeneity on nano-V2O5 film surface can be improved through proper increasing of annealing temperatures; The results of transmission and absorption spectra show that a red shift will occur at the absorption edges of V2O5 films, and optical band gaps are shortened gradually with the increase of annealing temperature.
The V2O5 thin film was prepared on the substrates of Si glass and commercial glass by the sol-gel technique. The samples prepared were annealed in air atmosphere at different temperatures. The microstructure, the morphology and optical properties of V2O5 thin films were studied by XRD, SEM and spectrophotometer. The results of XRD and SEM indicate that the better crystalline states and orientation with V2O5 (001) and (200) after annealing can be obtained, and the grain homogeneity on nano-V2O5 film surface can be improved through proper increasing of annealing temperatures; The results of transmission and absorption spectra show that a red shift will occur at the absorption edges of V2O5 films, and optical band gaps are shortened gradually with the increase of annealing temperature.
33 The peg-nail structure selective laser modification of plasma sprayed YSZ thermal barrier coatings
2017, 46(3):577-584.
Abstract:
In this paper, yttria partially stabilized zirconia (YSZ) thermal barrier coatings (TBCs) were deposited by air plasma spraying (APS) method on nickle-based superalloy with initially sprayed NiCoCrAlYTa bond coat. After that, the surface of the plasma sprayed TBCs was subjected to the peg-nail structure selective laser modification using a Nd:YAG pulsed laser. The microstructure and performance of the plasma sprayed and laser modified YSZ coatings were investigated. The results revealed that the peg-nail structure selective laser modification helped to reduce the surface roughness considerably, eliminate to surface porosities and produced a network of continuous cracks perpendicular to the surface. The microstructure of laser modified area consisted of columnar grains in the cross-section and equiaxed grains on the surface. XRD patterns showed that both as-sprayed and the peg-nail structure laser modified coatings consisted of nonequibrium tetragonal (T'') phase, however, monoclinic (M) phase disappeared and intensity of T'' phase slightly increased in the range of 72-76°（2θ) after the peg-nail structure laser modification. It has been found that the average bond strength YSZ coatings was enhanced from 7.3 MPa to 13.3 MPa after the peg-nail structure laser modification. Thermal insulation capability of the peg-nail structure laser modified TBCs, as compared to the as-sprayed TBCs, was decreased due to microstructure change in the ceramic top coat.
In this paper, yttria partially stabilized zirconia (YSZ) thermal barrier coatings (TBCs) were deposited by air plasma spraying (APS) method on nickle-based superalloy with initially sprayed NiCoCrAlYTa bond coat. After that, the surface of the plasma sprayed TBCs was subjected to the peg-nail structure selective laser modification using a Nd:YAG pulsed laser. The microstructure and performance of the plasma sprayed and laser modified YSZ coatings were investigated. The results revealed that the peg-nail structure selective laser modification helped to reduce the surface roughness considerably, eliminate to surface porosities and produced a network of continuous cracks perpendicular to the surface. The microstructure of laser modified area consisted of columnar grains in the cross-section and equiaxed grains on the surface. XRD patterns showed that both as-sprayed and the peg-nail structure laser modified coatings consisted of nonequibrium tetragonal (T'') phase, however, monoclinic (M) phase disappeared and intensity of T'' phase slightly increased in the range of 72-76°（2θ) after the peg-nail structure laser modification. It has been found that the average bond strength YSZ coatings was enhanced from 7.3 MPa to 13.3 MPa after the peg-nail structure laser modification. Thermal insulation capability of the peg-nail structure laser modified TBCs, as compared to the as-sprayed TBCs, was decreased due to microstructure change in the ceramic top coat.
2016, 45(11):2798-2803.
Abstract:
In situ 5wt.%Al3Zr/6063Al composites were fabricated by direct melt reaction method (DMR) and then processed by deformation pretreatment. Process of the pretreatment is forging of 70% deformation at 450℃ and friction stir processing (FSP). The high strain rate superplasticity of the composites was studied by modern analytic determination methods. The results show that the average grain size of the composites is less than 10 μm after forging and FSP. The composites exhibited superplasticity at the temperature of 350℃ to 500℃ and initial strain rate of 1.0×10-3s-1 to 1.0×10-1s-1. The elongation reached 330% and the sensitive index (m value) is 0.45 at the initial strain rate of 1.0×10-2s-1 and the temperature of 500 ℃. The dominant mechanisms of superplastic deformation were grain boundary sliding and dislocation slip which synergized with moderate grain growth and dynamic continuous recrystallization.
In situ 5wt.%Al3Zr/6063Al composites were fabricated by direct melt reaction method (DMR) and then processed by deformation pretreatment. Process of the pretreatment is forging of 70% deformation at 450℃ and friction stir processing (FSP). The high strain rate superplasticity of the composites was studied by modern analytic determination methods. The results show that the average grain size of the composites is less than 10 μm after forging and FSP. The composites exhibited superplasticity at the temperature of 350℃ to 500℃ and initial strain rate of 1.0×10-3s-1 to 1.0×10-1s-1. The elongation reached 330% and the sensitive index (m value) is 0.45 at the initial strain rate of 1.0×10-2s-1 and the temperature of 500 ℃. The dominant mechanisms of superplastic deformation were grain boundary sliding and dislocation slip which synergized with moderate grain growth and dynamic continuous recrystallization.
2017, 46(1):63-67.
Abstract:
W/ZrC cermets were fabricated by Displacive Compensation of Porosity (DCP) and Hot Pressing (HP), and then they were heat treated at 2600°C for 1 h. Microstructure changes of W/ZrC cermets before and after heat treatment were investigated. Results showed that both of two W/ZrC cermets had an increase of open porosity, a linear expansion and a weight loss after the heat treatment. Annealed DCP-derived W/ZrC cermets were still composed of dispersive W phases and continuous ZrC phases, but residual WC, W2C and Zr-Cu alloy were gone, instead, a large increase of pores and a sharp reduction of W phases appearing. While a new phase of W2C was formed in annealed HP-derived W/ZrC cermets, and W grains had a tendency to congregate together to form a big agglomerate phase.
W/ZrC cermets were fabricated by Displacive Compensation of Porosity (DCP) and Hot Pressing (HP), and then they were heat treated at 2600°C for 1 h. Microstructure changes of W/ZrC cermets before and after heat treatment were investigated. Results showed that both of two W/ZrC cermets had an increase of open porosity, a linear expansion and a weight loss after the heat treatment. Annealed DCP-derived W/ZrC cermets were still composed of dispersive W phases and continuous ZrC phases, but residual WC, W2C and Zr-Cu alloy were gone, instead, a large increase of pores and a sharp reduction of W phases appearing. While a new phase of W2C was formed in annealed HP-derived W/ZrC cermets, and W grains had a tendency to congregate together to form a big agglomerate phase.
2008, 37(1):10-13.
Abstract:
在Gleeble-1500热模拟试验机上进行热压缩试验,研究了变形温度为880～1080 ℃,应变速率为0.001～10 s-1的Ti53311S钛合金的热变形行为.根据应力应变曲线分析了该合金的热变形行为,计算分析了加工图,并观察了变形后的显微组织.利用加工图结合显微组织确定了热变形的流变失稳区和实验范围内的最佳变形参数.结果表明:Ti53311S钛合金加工过程中温度应控制在相变点以下,应变速率应控制在0.01 s-1以上和10 s-1以下为宜.
在Gleeble-1500热模拟试验机上进行热压缩试验,研究了变形温度为880～1080 ℃,应变速率为0.001～10 s-1的Ti53311S钛合金的热变形行为.根据应力应变曲线分析了该合金的热变形行为,计算分析了加工图,并观察了变形后的显微组织.利用加工图结合显微组织确定了热变形的流变失稳区和实验范围内的最佳变形参数.结果表明:Ti53311S钛合金加工过程中温度应控制在相变点以下,应变速率应控制在0.01 s-1以上和10 s-1以下为宜.
2016, 45(5):1168-1174.
Abstract:
The experiments of asymmetric and symmetric hot rolling were carried out to investigate the role of asymmetric hot rolling on microstructure and mechanical properties of titanium alloy by showing metallographic microstructure, mechanical property, fracture morphology and microscopic orientation. The results demonstrate that complex strain path is prior to monotonic strain path for refining grain and improving simultaneously the values of strength and ductility, and the grain size in asymmetric rolled specimen surface is smaller than that in specimen center. Asymmetric hot rolling could refine grain compared with symmetric hot rolling. The values of strength and ductility of asymmetric rolled specimen is higher than that of symmetric rolled specimen, and the values of strength and ductility increase with the development of roll speed ratio. The plastic deformation mechanism of asymmetric rolled specimen may be slip. While, the one of symmetric rolled specimen are twin and slip.
The experiments of asymmetric and symmetric hot rolling were carried out to investigate the role of asymmetric hot rolling on microstructure and mechanical properties of titanium alloy by showing metallographic microstructure, mechanical property, fracture morphology and microscopic orientation. The results demonstrate that complex strain path is prior to monotonic strain path for refining grain and improving simultaneously the values of strength and ductility, and the grain size in asymmetric rolled specimen surface is smaller than that in specimen center. Asymmetric hot rolling could refine grain compared with symmetric hot rolling. The values of strength and ductility of asymmetric rolled specimen is higher than that of symmetric rolled specimen, and the values of strength and ductility increase with the development of roll speed ratio. The plastic deformation mechanism of asymmetric rolled specimen may be slip. While, the one of symmetric rolled specimen are twin and slip.
2017, 46(2):296-300.
Abstract:
The corrosion behavior of Gd56Al26Co18 and Sm56Al26Co18 amorphous alloys in 0.01 M NaOH solution had been researched by polarization scanning, EIS technique, XRD and SEM. The free volume was also investigated by DSC technique. It was found that the corrosion resistance of amorphous alloys increased after remelting.
The corrosion behavior of Gd56Al26Co18 and Sm56Al26Co18 amorphous alloys in 0.01 M NaOH solution had been researched by polarization scanning, EIS technique, XRD and SEM. The free volume was also investigated by DSC technique. It was found that the corrosion resistance of amorphous alloys increased after remelting.
2009, 38(3):384-388.
Abstract:
A layer of TiO2 film was prepared by sol-gel method on the surface of TLM(Ti-3Zr-2Sn-3Mo-25Nb) alloy. Then the coated samples were treated by hydroxyl solution and amination solution in order to introduce the OH- and NH2- active groups, and the heparin was linked on the surface of TiO2 film through these active groups. The phase identification and the surface characteristics of the samples were successively undertaken using XRD, SEM and EDS. The in vitro blood compatibility of the TLM alloy specimens with and without heparinization treatments was evaluated by the contact angle test, the hemolysis test and investigation of their platelet adhesion behavior. The results showed that the haemocompatibility of the TLM alloy could be significantly improved by surface modification via heparinization.
A layer of TiO2 film was prepared by sol-gel method on the surface of TLM(Ti-3Zr-2Sn-3Mo-25Nb) alloy. Then the coated samples were treated by hydroxyl solution and amination solution in order to introduce the OH- and NH2- active groups, and the heparin was linked on the surface of TiO2 film through these active groups. The phase identification and the surface characteristics of the samples were successively undertaken using XRD, SEM and EDS. The in vitro blood compatibility of the TLM alloy specimens with and without heparinization treatments was evaluated by the contact angle test, the hemolysis test and investigation of their platelet adhesion behavior. The results showed that the haemocompatibility of the TLM alloy could be significantly improved by surface modification via heparinization.
2008, 37(1):24-28.
Abstract:
采用透射电子显微镜(TEM)研究了两相钛合金Ti-700在不同热处理制度下的显微组织和相结构.探讨了固溶温度,冷却方式以及时效处理对显微结构的影响.结果表明,在所选择的热处理制度下,合金为双态组织,除了基体(α β)外,还发现了α2相以及调质结构.这些析出物对Ti-700钛合金的性能有一定影响.
采用透射电子显微镜(TEM)研究了两相钛合金Ti-700在不同热处理制度下的显微组织和相结构.探讨了固溶温度,冷却方式以及时效处理对显微结构的影响.结果表明,在所选择的热处理制度下,合金为双态组织,除了基体(α β)外,还发现了α2相以及调质结构.这些析出物对Ti-700钛合金的性能有一定影响.
2009, 38(8):1402-1405.
Abstract:
The change and its mechanism of the infrared emissivity of superalloy K424 with deposited Au film before and after heat treatment were investigated. XRD analyses show that the metal elements of the substrate diffused from the alloy into the Au film, and mainly formed the solid solution of Cr in Au, i.e. Au0.7Cr0.3. EDXS analyses show that oxides of substrate metal element were formed on the rough surface of the sample with deposited Au film after heat treatment; while the polished surface of the sample was still Au film. Both the surface state and heat treatment have great influence on the infrared emissivity tested by spectral radiometer, SR5000.
The change and its mechanism of the infrared emissivity of superalloy K424 with deposited Au film before and after heat treatment were investigated. XRD analyses show that the metal elements of the substrate diffused from the alloy into the Au film, and mainly formed the solid solution of Cr in Au, i.e. Au0.7Cr0.3. EDXS analyses show that oxides of substrate metal element were formed on the rough surface of the sample with deposited Au film after heat treatment; while the polished surface of the sample was still Au film. Both the surface state and heat treatment have great influence on the infrared emissivity tested by spectral radiometer, SR5000.
2009, 38(3):426-430.
Abstract:
Transverse mechanical properties of TMCs reinforced by two types of SiC fibers with and without C coating were determined by use of cross-shaped specimens. The initial nonlinear stress of the stress-strain curve under the applied transverse tensile load was adopted to calculate the interface strength. The interface strength with C coating was 53 MPa which was lower than 196 MPa of the one without C coating. The debonding position of two interface were different, i.e. the former was between the fiber and C coating, but the latter was between the matrix and reaction products. The initial nonlinearity stress of TMCs reinforced by multiple fibers with 30% volume fraction was lower than that of single fiber reinforced TMCs, which was caused by the decrease of residual stress on the surface of fiber, and the interface strength was not influenced by the more additional fibers
Transverse mechanical properties of TMCs reinforced by two types of SiC fibers with and without C coating were determined by use of cross-shaped specimens. The initial nonlinear stress of the stress-strain curve under the applied transverse tensile load was adopted to calculate the interface strength. The interface strength with C coating was 53 MPa which was lower than 196 MPa of the one without C coating. The debonding position of two interface were different, i.e. the former was between the fiber and C coating, but the latter was between the matrix and reaction products. The initial nonlinearity stress of TMCs reinforced by multiple fibers with 30% volume fraction was lower than that of single fiber reinforced TMCs, which was caused by the decrease of residual stress on the surface of fiber, and the interface strength was not influenced by the more additional fibers
2009, 38(3):434-438.
Abstract:
By means of calculating the elements diffusion mobility and γ￠-phase directional coarsening rate of Ni-Cr-Co-W-Mo-Al-Ta single crystal superalloys with different compositions, the effect of element reaction on the rate of element diffusion and γ￠-phase directional coarsening was studied. Results show that during the γ￠-phase directional coarsening period, the rafted rate of γ￠-phase changes with composition and stress, and the rafted time is decreased with the stress increasing. The driving force of the elements diffusion and γ￠-phase directional coarsening during tensile creep are related to the applied stress and elastic modulus. Element reaction has effect on the diffusion rate of Al. As the total content of Ta+Mo and the ratio of Ta/W increased, the diffusion activation energy of Al is increased and diffusion rate decreased, and the rafted time of γ￠-phase is elongated. In the diffusion field of γ￠-phase directional coarsening, the formation of γ￠-order phase is attributed to the concentration of the atoms Al and Ta, which is a spontaneous process of the decreased free energy. The Al, Ta atoms with bigger radius are diffused to {100} planes to form the stable arranging order and the linking bond of the atoms with different kinds, which is a main reason of γ￠-order phase formation with Ll2 structure
By means of calculating the elements diffusion mobility and γ￠-phase directional coarsening rate of Ni-Cr-Co-W-Mo-Al-Ta single crystal superalloys with different compositions, the effect of element reaction on the rate of element diffusion and γ￠-phase directional coarsening was studied. Results show that during the γ￠-phase directional coarsening period, the rafted rate of γ￠-phase changes with composition and stress, and the rafted time is decreased with the stress increasing. The driving force of the elements diffusion and γ￠-phase directional coarsening during tensile creep are related to the applied stress and elastic modulus. Element reaction has effect on the diffusion rate of Al. As the total content of Ta+Mo and the ratio of Ta/W increased, the diffusion activation energy of Al is increased and diffusion rate decreased, and the rafted time of γ￠-phase is elongated. In the diffusion field of γ￠-phase directional coarsening, the formation of γ￠-order phase is attributed to the concentration of the atoms Al and Ta, which is a spontaneous process of the decreased free energy. The Al, Ta atoms with bigger radius are diffused to {100} planes to form the stable arranging order and the linking bond of the atoms with different kinds, which is a main reason of γ￠-order phase formation with Ll2 structure
2009, 38(9):1505-1508.
Abstract:
A novel type of foundry method for TiAl-based alloy is presented in the present paper. The filling processes of Ti-47Al alloy sheet and blade have been studied via numerical simulation. The investigation results indicate that the filling fraction is enhanced by the increase of filling velocity and graphite throat diameter. The graphite throat diameter is the main parameter for the backward filling location in the process of vacuum suction casting. With the increase of mould temperature, the solid fraction is reduced. The alloy solidification begins from bottom to top. The TiAl sheet and the blade are produced by this method. The grain size of the sheet is in the range from 10 μm to 40 μm. There is no obvious shrinkage cavity
A novel type of foundry method for TiAl-based alloy is presented in the present paper. The filling processes of Ti-47Al alloy sheet and blade have been studied via numerical simulation. The investigation results indicate that the filling fraction is enhanced by the increase of filling velocity and graphite throat diameter. The graphite throat diameter is the main parameter for the backward filling location in the process of vacuum suction casting. With the increase of mould temperature, the solid fraction is reduced. The alloy solidification begins from bottom to top. The TiAl sheet and the blade are produced by this method. The grain size of the sheet is in the range from 10 μm to 40 μm. There is no obvious shrinkage cavity
Wang Jie
,
Xu Youlong
,
Ma Jianhua
,
Zhang Xuanhong
,
Meng Linbin
,
Shi Hongfu
,
Jiang Chunqiang
,
Peng Dan
2012, 41(8):1467-1471.
Abstract:
Nanostructured hydrous ruthenium oxide (RuO2·xH2O) was directly deposited on tantalum (Ta) substrates by cyclic voltammetry (CV) technology in RuCl3·xH2O aqueous solutions. The growth mechanism, revealed by energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) techniques, is that Ru3+ ions are reduced to nanostructured ruthenium (Ru) particles during negative potential scanning, then are oxidized to RuO2·xH2O granules (also in nanometers) during the following positive scanning. The unique nanometer structure of RuO2·xH2O, rather than the conventional “mud-cracked” structure, enable itself a high specific capacitance of 730 F·g-1 at a scanning rate of 50 mV·s-1 and a very fast charging/discharging ability. The speci?c capacitance is still up to 700 F·g-1 when the oxide loading is up to 1.2 mg·cm?2. In addition, the capacitance retains about 100% after 100,000 charging/discharging cycles. All of these indicate that the nanosized RuO2·xH2O is an excellent electrode material for energy storage and conversion devices, such as supercapacitors
Nanostructured hydrous ruthenium oxide (RuO2·xH2O) was directly deposited on tantalum (Ta) substrates by cyclic voltammetry (CV) technology in RuCl3·xH2O aqueous solutions. The growth mechanism, revealed by energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) techniques, is that Ru3+ ions are reduced to nanostructured ruthenium (Ru) particles during negative potential scanning, then are oxidized to RuO2·xH2O granules (also in nanometers) during the following positive scanning. The unique nanometer structure of RuO2·xH2O, rather than the conventional “mud-cracked” structure, enable itself a high specific capacitance of 730 F·g-1 at a scanning rate of 50 mV·s-1 and a very fast charging/discharging ability. The speci?c capacitance is still up to 700 F·g-1 when the oxide loading is up to 1.2 mg·cm?2. In addition, the capacitance retains about 100% after 100,000 charging/discharging cycles. All of these indicate that the nanosized RuO2·xH2O is an excellent electrode material for energy storage and conversion devices, such as supercapacitors
2012, 41(6):941-946.
Abstract:
Ultrafine-grained (UFG) metal materials processed by severe plastic deformation (SPD) have attracted the great interest. This overview introduces some attractive SPD techniques. Special attention is paid to two new deformation techniques named Elliptical Cross-section Spiral Channel Extrusion with Equal-area (ECSEE) and Elliptical Cross-section Spiral Channel Drawing with Equal-area (ECSDE). The mechanism and microstructure transformation characteristics of materials in SPD, current problems and ongoing research are also discussed in detail
Ultrafine-grained (UFG) metal materials processed by severe plastic deformation (SPD) have attracted the great interest. This overview introduces some attractive SPD techniques. Special attention is paid to two new deformation techniques named Elliptical Cross-section Spiral Channel Extrusion with Equal-area (ECSEE) and Elliptical Cross-section Spiral Channel Drawing with Equal-area (ECSDE). The mechanism and microstructure transformation characteristics of materials in SPD, current problems and ongoing research are also discussed in detail
2010, 39(2):229-233.
Abstract:
Using the first-principles pseudopotential plane-wave methods based on the density functional theory, the elastic constants of B2-(Ni1-xFex)Al (x=0-3.0 at%) supercells with or without Ni vacancy or Ni anti-site defect were calculated in the framework of Virtual Crystal Approximation. Several parameters, such as elastic constant C44, Cauchy pressure (C12-C44), Young modulus E, the shear modulus G and their ratio G/B0, have been adopted to characterize and assess the effect of Fe alloying concentration on the ductility and hardness of NiAl intermetallic compounds. It is found that Fe addition with x < 0.6 at% is proved to be efficient to enforce the strength or hardness of NiAl intermetallic compounds either for perfect crystals or for defect crystals. No improvement of the ductility of perfect B2-NiAl crystals can be demonstrated as Fe is added in the range from 0 to 3.0 at%. The Ni vacancy or Ni anti-site defects make the intrinsic ductility of perfect B2-NiAl crystals without Fe addition to be weakened. However, an obvious decrease in the degree of the embrittlement of B2-(Ni1-xFex)Al crystals with Ni vacancies can be seen as Fe alloying concentration x is lower than 0.5 at%, and the optimum additions locate in the range from 0.2 at% to 0.4 at%. From these calculations, a deduction therefore is conduced. That is for the distinct increase in the elongation rate of a B2-NiAl single crystal with Fe addition of 0.20-0.25 at% in the experiments could originate from the correlative and cooperative effects between vacancies and Fe addition in the B2-NiAl crystal
Using the first-principles pseudopotential plane-wave methods based on the density functional theory, the elastic constants of B2-(Ni1-xFex)Al (x=0-3.0 at%) supercells with or without Ni vacancy or Ni anti-site defect were calculated in the framework of Virtual Crystal Approximation. Several parameters, such as elastic constant C44, Cauchy pressure (C12-C44), Young modulus E, the shear modulus G and their ratio G/B0, have been adopted to characterize and assess the effect of Fe alloying concentration on the ductility and hardness of NiAl intermetallic compounds. It is found that Fe addition with x < 0.6 at% is proved to be efficient to enforce the strength or hardness of NiAl intermetallic compounds either for perfect crystals or for defect crystals. No improvement of the ductility of perfect B2-NiAl crystals can be demonstrated as Fe is added in the range from 0 to 3.0 at%. The Ni vacancy or Ni anti-site defects make the intrinsic ductility of perfect B2-NiAl crystals without Fe addition to be weakened. However, an obvious decrease in the degree of the embrittlement of B2-(Ni1-xFex)Al crystals with Ni vacancies can be seen as Fe alloying concentration x is lower than 0.5 at%, and the optimum additions locate in the range from 0.2 at% to 0.4 at%. From these calculations, a deduction therefore is conduced. That is for the distinct increase in the elongation rate of a B2-NiAl single crystal with Fe addition of 0.20-0.25 at% in the experiments could originate from the correlative and cooperative effects between vacancies and Fe addition in the B2-NiAl crystal
48 Research of heat treatment on the microstructure and mechanical properties of a Nb-base superalloy
2017, 46(8):2260-2265.
Abstract:
The effect of heat treatment on the microstructure and mechanical properties of an Nbss/Nb5Si3 in situ composites prepared by HRS method was investigated. The microstructure evolution of samples during heat treatment process were analysed by SEM、XRD and EPMA: the result showesd that the as-cast alloy consisted of Nbss、γ-Nb5Si3 、β-Nb5Si3 and primary carbide phase; after heat treatment, the β-(Nb,Ti)5Si3 phase was transformed to α-(Nb,Ti)5Si3 phase and the secondary carbide was precipitated. Meanwhile, the silicide phase gradually dissolved or broken into small pieces, with the morphology changing from the needle into granules. The transformation (Nb,Ti)5Si3 →(Ti,Nb)5Si3 occurred when aging at 1150℃.The compressive strength and room temperature tensile strength of heat-treatment specimens were improved, while the tensile strength of as-cast and heat-treated samples at 1000℃ was at same level. The temperature has a great influence on the fracture mode, cleavage fracture at low temperature and ductile fracture at high temperature.
The effect of heat treatment on the microstructure and mechanical properties of an Nbss/Nb5Si3 in situ composites prepared by HRS method was investigated. The microstructure evolution of samples during heat treatment process were analysed by SEM、XRD and EPMA: the result showesd that the as-cast alloy consisted of Nbss、γ-Nb5Si3 、β-Nb5Si3 and primary carbide phase; after heat treatment, the β-(Nb,Ti)5Si3 phase was transformed to α-(Nb,Ti)5Si3 phase and the secondary carbide was precipitated. Meanwhile, the silicide phase gradually dissolved or broken into small pieces, with the morphology changing from the needle into granules. The transformation (Nb,Ti)5Si3 →(Ti,Nb)5Si3 occurred when aging at 1150℃.The compressive strength and room temperature tensile strength of heat-treatment specimens were improved, while the tensile strength of as-cast and heat-treated samples at 1000℃ was at same level. The temperature has a great influence on the fracture mode, cleavage fracture at low temperature and ductile fracture at high temperature.
2010, 39(2):234-237.
Abstract:
FeMnCr/Cr3C2 cored wire was developed for building up the erosion-resistant coatings of super-critical boiler pipes by means of High-Velocity Arc Spraying. The high-temperature erosion behaviors at different impact angles of FeMnCr/Cr3C2 coatings were studied and compared with those of FeCrNi/Cr3C2 coatings and 20 steel by optical microscopy, scanning electron microscopy and energy dispersion spectrum analysis. Results show that FeMnCr/Cr3C2 coatings have the maximum erosive rate when the impact angle is about 60° due to the semi-brittleness erosion mechanism for FeMnCr/Cr3C2 coatings. The erosion resistance of FeMnCr/Cr3C2 coatings is closed to that of FeCrNi/Cr3C2 coatings, and obviously better than that of 20 steel.
FeMnCr/Cr3C2 cored wire was developed for building up the erosion-resistant coatings of super-critical boiler pipes by means of High-Velocity Arc Spraying. The high-temperature erosion behaviors at different impact angles of FeMnCr/Cr3C2 coatings were studied and compared with those of FeCrNi/Cr3C2 coatings and 20 steel by optical microscopy, scanning electron microscopy and energy dispersion spectrum analysis. Results show that FeMnCr/Cr3C2 coatings have the maximum erosive rate when the impact angle is about 60° due to the semi-brittleness erosion mechanism for FeMnCr/Cr3C2 coatings. The erosion resistance of FeMnCr/Cr3C2 coatings is closed to that of FeCrNi/Cr3C2 coatings, and obviously better than that of 20 steel.
2009, 38(2):189-192.
Abstract:
HfO2 gate dielectric films with a blocking layer of Al2O3 inserted between HfO2 layer and Si layer (HfO2/Si) were treated with rapid thermal annealing process at 700 ℃. The interfacial structure and electrical properties were reported. The results of X-ray photoelectron spectroscopy showed that the interfacial layer of SiOx transformed into SiO2 after the annealing treatment, and Hf-silicates and Hf-silicides were not detected. The results of high-resolution transmission electron microscopy indicated that the interfacial layer was composed of SiO2 for the annealed film with blocking layer. The results of the electrical measurements indicated that the equivalent oxide thickness decreased to 2.5 nm and the fixed charge density decreased to –4.5×1011/cm2 in comparison with the same thickness of HfO2 films without the blocking layer. Al2O3 layer could effectively prevent the diffusion of Si into HfO2 film and improve the interfacial and electrical performance of HfO2 film
HfO2 gate dielectric films with a blocking layer of Al2O3 inserted between HfO2 layer and Si layer (HfO2/Si) were treated with rapid thermal annealing process at 700 ℃. The interfacial structure and electrical properties were reported. The results of X-ray photoelectron spectroscopy showed that the interfacial layer of SiOx transformed into SiO2 after the annealing treatment, and Hf-silicates and Hf-silicides were not detected. The results of high-resolution transmission electron microscopy indicated that the interfacial layer was composed of SiO2 for the annealed film with blocking layer. The results of the electrical measurements indicated that the equivalent oxide thickness decreased to 2.5 nm and the fixed charge density decreased to –4.5×1011/cm2 in comparison with the same thickness of HfO2 films without the blocking layer. Al2O3 layer could effectively prevent the diffusion of Si into HfO2 film and improve the interfacial and electrical performance of HfO2 film
2012, 41(1):184-188.
Abstract:
Kinds of noble metal catalysts, and the influencing factors of catalytic activity, such as preparation methods, carriers, particle size and the structure of active center have been summarized. Meanwhile, the appropriate reactions of the noble metal catalysts have been introduced.
Kinds of noble metal catalysts, and the influencing factors of catalytic activity, such as preparation methods, carriers, particle size and the structure of active center have been summarized. Meanwhile, the appropriate reactions of the noble metal catalysts have been introduced.
52 Microstructure Comparison between Co-Sputtered and Multilayer-Sputtered FePt:Ag Granular Thin Films
2005, 34(12):1879-1881.
Abstract:
Two different sputtering modes, co-sputtering and multilayer-sputtering, were used to fabricate FePt:Ag granular thin films. It is observed by the MFM and TEM images that smaller magnetic domain patterns and grains are more uniformly distributed in the co-sputtered granular films compared to in multilayer-sputtered ones. This difference in the microstructure is explained to be attributed to the more randomly distributed Ag atoms in the co-sputtered films. Further study on in-depth defects in these films confirms this explanation.
Two different sputtering modes, co-sputtering and multilayer-sputtering, were used to fabricate FePt:Ag granular thin films. It is observed by the MFM and TEM images that smaller magnetic domain patterns and grains are more uniformly distributed in the co-sputtered granular films compared to in multilayer-sputtered ones. This difference in the microstructure is explained to be attributed to the more randomly distributed Ag atoms in the co-sputtered films. Further study on in-depth defects in these films confirms this explanation.
2010, 39(2):347-351.
Abstract:
A three dimensional finite element mathematical model of electromagnetic field and temperature field was developed to investigate the effect of high frequency amplitude-modulated magnetic field on the billet surface temperature. The results show that the induction heat power of magnetic field amplitude-modulated with sine wave and square wave is unrelated to the frequency of modulating wave. The induction heat power of magnetic field modulated with square wave is between the induction heat powers of the two constant amplitude magnetic fields employed to modulate. If the induction heat powers of the two constant amplitude magnetic fields are determined, the induction heat power of magnetic fields modulated with square wave is determined by the relative scale of the acting time of the two constant amplitude magnetic fields. The induction heat power of magnetic field modulated with sine wave is about 62-64% of that of the high frequency magnetic field before modulation
A three dimensional finite element mathematical model of electromagnetic field and temperature field was developed to investigate the effect of high frequency amplitude-modulated magnetic field on the billet surface temperature. The results show that the induction heat power of magnetic field amplitude-modulated with sine wave and square wave is unrelated to the frequency of modulating wave. The induction heat power of magnetic field modulated with square wave is between the induction heat powers of the two constant amplitude magnetic fields employed to modulate. If the induction heat powers of the two constant amplitude magnetic fields are determined, the induction heat power of magnetic fields modulated with square wave is determined by the relative scale of the acting time of the two constant amplitude magnetic fields. The induction heat power of magnetic field modulated with sine wave is about 62-64% of that of the high frequency magnetic field before modulation
2013, 42(6):1291-1294.
Abstract:
Spherical micro-sized titanium powder was synthesized by (RF) plasma with large TiH2 powder as starting material. The phase, morphology and particle size distribution of the powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser micron sizer (LMS), respectively. The dehydrogenation, hydrogen decrepitation and spheroidization of TiH2 feedstock take place in one-step by RF plasma processing and the prepared spherical powder possesses favorable dispersity and smooth surface. The prepared fine spherical powder is composed of Ti and residual TiH. Pure single-phase spherical titanium powder is obtained after further vacuum (1.3×10-4 Pa) dehydrogenation treatment at 750 oC for 2 h. The average size of Ti powder is reduced from 100~150 μm of TiH2 powders to 20~50 μm after the treatment in the plasma. The spheroidization efficiency is almost 100% at feeding rate of 15 g/min. The RF plasma-assisted argon dehydrogenation and decomposition of TiH2 is an ideal route for large-scale synthesis of well- spherical metallic titanium powder.
Spherical micro-sized titanium powder was synthesized by (RF) plasma with large TiH2 powder as starting material. The phase, morphology and particle size distribution of the powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser micron sizer (LMS), respectively. The dehydrogenation, hydrogen decrepitation and spheroidization of TiH2 feedstock take place in one-step by RF plasma processing and the prepared spherical powder possesses favorable dispersity and smooth surface. The prepared fine spherical powder is composed of Ti and residual TiH. Pure single-phase spherical titanium powder is obtained after further vacuum (1.3×10-4 Pa) dehydrogenation treatment at 750 oC for 2 h. The average size of Ti powder is reduced from 100~150 μm of TiH2 powders to 20~50 μm after the treatment in the plasma. The spheroidization efficiency is almost 100% at feeding rate of 15 g/min. The RF plasma-assisted argon dehydrogenation and decomposition of TiH2 is an ideal route for large-scale synthesis of well- spherical metallic titanium powder.
2010, 39(2):224-228.
Abstract:
The creep experiment of Ti40 alloy after annealing treatment at 600 ℃ for 4 h was carried on in a temperature range from 500 ℃ to 550 ℃ with various stresses. The experimental results indicate that the creep behavior can be analyzed in two temperature intervals in this creep temperature range. The first temperature interval is ranging from 500 ℃ to 520 ℃; the second one is ranging from 535 ℃ to 550 ℃. In different temperature intervals, the alloy has different creep constitutive equations. Judging by the analysis, it is deduced that the stress has obvious effect on dislocations glide and climbing controlled by heat activation when the temperature interval was at lower temperatures (500-520 ℃). With increasing temperature, the diffusion has more and more effect on the creep deformation. In higher temperature range (535-550 ℃), the creep deformation may be determined by self-diffusion or alloying element diffusion
The creep experiment of Ti40 alloy after annealing treatment at 600 ℃ for 4 h was carried on in a temperature range from 500 ℃ to 550 ℃ with various stresses. The experimental results indicate that the creep behavior can be analyzed in two temperature intervals in this creep temperature range. The first temperature interval is ranging from 500 ℃ to 520 ℃; the second one is ranging from 535 ℃ to 550 ℃. In different temperature intervals, the alloy has different creep constitutive equations. Judging by the analysis, it is deduced that the stress has obvious effect on dislocations glide and climbing controlled by heat activation when the temperature interval was at lower temperatures (500-520 ℃). With increasing temperature, the diffusion has more and more effect on the creep deformation. In higher temperature range (535-550 ℃), the creep deformation may be determined by self-diffusion or alloying element diffusion
2016, 45(5):1128-1131.
Abstract:
NiTi alloy was subjected to one-step hydrothermal treatment in the concentrated CaHPO4 and Ca(H2PO4)2 solutions for bioactive surface modification. The treated samples are covered by films composed of fine grains (~70 nm) and large particles (100-250 nm). XPS analysis shows that Ti at the surface presents as TiO2, Ni is not detectable, and Ca and P are in the form of calcium phosphate. X-ray diffraction peaks of anatase TiO2 and hydroxyapatite are present for the treated samples. Potentiodynamic polarization test in a Ca-free Hank’s balanced solution reveals that the treated sample has markedly improved corrosion resistance compared with the polished sample. The present work would provide a one-step bioactive surface modification method that is easily-operated, low-temperatured, less corrosive, and potentially suitable for biomedical porous NiTi alloy.
NiTi alloy was subjected to one-step hydrothermal treatment in the concentrated CaHPO4 and Ca(H2PO4)2 solutions for bioactive surface modification. The treated samples are covered by films composed of fine grains (~70 nm) and large particles (100-250 nm). XPS analysis shows that Ti at the surface presents as TiO2, Ni is not detectable, and Ca and P are in the form of calcium phosphate. X-ray diffraction peaks of anatase TiO2 and hydroxyapatite are present for the treated samples. Potentiodynamic polarization test in a Ca-free Hank’s balanced solution reveals that the treated sample has markedly improved corrosion resistance compared with the polished sample. The present work would provide a one-step bioactive surface modification method that is easily-operated, low-temperatured, less corrosive, and potentially suitable for biomedical porous NiTi alloy.
2010, 39(1):85-89.
Abstract:
spicule and flake with big sizes on the surface of the milling-free powders, while on the surface of milled powders ZnO was shaped mainly as spicule with small sizes. Nodules of virtually pure silver atoms formed on the surface of powder during internal oxidation, which is attributed to the compressive stress caused by the expansion of ZnO in the silver-matrix during internal oxidation.
spicule and flake with big sizes on the surface of the milling-free powders, while on the surface of milled powders ZnO was shaped mainly as spicule with small sizes. Nodules of virtually pure silver atoms formed on the surface of powder during internal oxidation, which is attributed to the compressive stress caused by the expansion of ZnO in the silver-matrix during internal oxidation.
2016, 45(5):1111-1116.
Abstract:
The microstructural evolution and mechanical properties of Mg-6Zn-1Mn-4Sn-0.5Y wrought alloy extruded at 360 and 420℃ were investigated by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), electron back scattered diffraction (EBSD) and tensile test. The results shown that the phase compositions of as-cast and extruded alloys were α-Mg, Mn, Mg7Zn3, Mg2Sn, and MgSnY phases. As the extrusion temperature increased from 360 to 420℃, dynamic recrystallization completed and grain growth occurred. The yield strength, ultimate tensile strength and elongation decreased from 259MPa, 350MPa and 18.3% to 239MPa, 332MPa and 12.5%, respectively. The theoretical values combined with the experimental values revealed that grain size strengthening and solid solution strengthening played the dominating role in the enhancement of yield strength.
The microstructural evolution and mechanical properties of Mg-6Zn-1Mn-4Sn-0.5Y wrought alloy extruded at 360 and 420℃ were investigated by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), electron back scattered diffraction (EBSD) and tensile test. The results shown that the phase compositions of as-cast and extruded alloys were α-Mg, Mn, Mg7Zn3, Mg2Sn, and MgSnY phases. As the extrusion temperature increased from 360 to 420℃, dynamic recrystallization completed and grain growth occurred. The yield strength, ultimate tensile strength and elongation decreased from 259MPa, 350MPa and 18.3% to 239MPa, 332MPa and 12.5%, respectively. The theoretical values combined with the experimental values revealed that grain size strengthening and solid solution strengthening played the dominating role in the enhancement of yield strength.
2009, 38(10):1815-1817.
Abstract:
Nitrogen-doped modified TiO2 films were prepared through sol-gel method. The thickness, surface microstructure and composition were analyzed by nano indenter, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of N-doped TiO2 films was researched through the degradation experiment of methylene blue under UV light. Results showed that nitrogen ions are doped into TiO2 films by adding urea and they are between TiO2 crystal lattices and mainly in interstitial configuration and substitution configuration. The films are very flat with the thickness of between 50-200 nm. Nitrogen ions doping improves the photocatalytic activity of TiO2 films. When N/Ti=0.015 (atom ratio) in TiO2 films, it takes single N-doped TiO2 film 2.5 h to decompose the methylene blue solution.
Nitrogen-doped modified TiO2 films were prepared through sol-gel method. The thickness, surface microstructure and composition were analyzed by nano indenter, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of N-doped TiO2 films was researched through the degradation experiment of methylene blue under UV light. Results showed that nitrogen ions are doped into TiO2 films by adding urea and they are between TiO2 crystal lattices and mainly in interstitial configuration and substitution configuration. The films are very flat with the thickness of between 50-200 nm. Nitrogen ions doping improves the photocatalytic activity of TiO2 films. When N/Ti=0.015 (atom ratio) in TiO2 films, it takes single N-doped TiO2 film 2.5 h to decompose the methylene blue solution.
2009, 38(11):1916-1919.
Abstract:
Differential scanning calorimetry (DSC) method and metallographic observation method have been adapted for the measurement of α＋β/β transformation temperatures of α titanium alloy TA7, α＋β titanium alloy TC4 and near β titanium alloy Ti-1023, and the coincidence has been discussed in the present paper. For the TA7 alloy, an obvious endothermic peak which covers a temperature range of about 60 ℃ occurred during α＋β/β transformation. The transformation temperature defined by the peak of first order derivative of the DSC curve was much near the temperature determined by the metallographic observation method. For the alloys TC4 and Ti-1023, on the other hand, only little baseline shifts which cover a temperature range of about 10~15 ℃ was observed during transformation. A better coincidence with the metallographic observation method was achieved for the alloys TC4 and Ti-1023 owing to the much narrow transformation temperature range.
Differential scanning calorimetry (DSC) method and metallographic observation method have been adapted for the measurement of α＋β/β transformation temperatures of α titanium alloy TA7, α＋β titanium alloy TC4 and near β titanium alloy Ti-1023, and the coincidence has been discussed in the present paper. For the TA7 alloy, an obvious endothermic peak which covers a temperature range of about 60 ℃ occurred during α＋β/β transformation. The transformation temperature defined by the peak of first order derivative of the DSC curve was much near the temperature determined by the metallographic observation method. For the alloys TC4 and Ti-1023, on the other hand, only little baseline shifts which cover a temperature range of about 10~15 ℃ was observed during transformation. A better coincidence with the metallographic observation method was achieved for the alloys TC4 and Ti-1023 owing to the much narrow transformation temperature range.
61 Thermodynamic Calculation of the Precipitation Reaction of MgZn Phase in Mg-6Zn-1Mn Magnesium Alloy
2009, 38(11):1940-1944.
Abstract:
Based on the Miedema model and the Toop model, the activities of Mg and Zn in the Mg-6Zn-1Mn alloy were calculated by a thermodynamic calculation model for predicting the precipitation behaviors of the intermetallic compounds in ternary metallic alloys. The relationship between the temperatures and the Gibbs free energy change during the precipitation reaction of the primary strengthening phase MgZn was deduced. According to the calculation, the precipitating temperature of MgZn phase is 580 K, in good agreement with the homogenizing temperature of this alloy and approved by our thermal analysis experimental results
Based on the Miedema model and the Toop model, the activities of Mg and Zn in the Mg-6Zn-1Mn alloy were calculated by a thermodynamic calculation model for predicting the precipitation behaviors of the intermetallic compounds in ternary metallic alloys. The relationship between the temperatures and the Gibbs free energy change during the precipitation reaction of the primary strengthening phase MgZn was deduced. According to the calculation, the precipitating temperature of MgZn phase is 580 K, in good agreement with the homogenizing temperature of this alloy and approved by our thermal analysis experimental results
2017, 46(3):699-703.
Abstract:
High strength and high conductivity Cu-Nb microcomposites are with nano-structured Nb fibers and pure Cu matrix. Strength size effect has been observed. The rule of strength changing with the size of Nb filaments was analyzed by stress-strain curves. The characteristics of elastic modulus and nano-indention hardness varying with the thickness of Nb filaments are investigated by nanoindentation. It is shown that the measured value of strength is considerably higher than that obtained by ROM and the UTS of Cu-Nb increases exponentially with the decreasing of dNb. Moreover, the nano-indention hardness of Nb filaments also increases greatly as the size dreased. It is believed that electronic interface scattering associated with the mean free path of the electrons is the main factor of Cu-Nb conductivity.
High strength and high conductivity Cu-Nb microcomposites are with nano-structured Nb fibers and pure Cu matrix. Strength size effect has been observed. The rule of strength changing with the size of Nb filaments was analyzed by stress-strain curves. The characteristics of elastic modulus and nano-indention hardness varying with the thickness of Nb filaments are investigated by nanoindentation. It is shown that the measured value of strength is considerably higher than that obtained by ROM and the UTS of Cu-Nb increases exponentially with the decreasing of dNb. Moreover, the nano-indention hardness of Nb filaments also increases greatly as the size dreased. It is believed that electronic interface scattering associated with the mean free path of the electrons is the main factor of Cu-Nb conductivity.
2009, 38(6):955-957.
Abstract:
The deformed microstructures and mechanical properties of commercial pure titanium (CP-Ti) with an initial grain size of about 28 μm was investigated using equal channel angular pressing (ECAP). ECAP was conducted at room temperature adopting a die with a channel angle of 120° via route BC. Special attention was paid on the microstructure evolution and mechanical properties of the ECAP samples. Deformation twins were found in most grains after the first and second pass of ECAP. After four ECAP passes, the original grains were refined from 28 μm to about 250 nm, and the ultimate strength and microhardness were significantly enhanced to 773 MPa and 2486 MPa, respectively. Meanwhile good ductility of 16.8% elongation still remained.
The deformed microstructures and mechanical properties of commercial pure titanium (CP-Ti) with an initial grain size of about 28 μm was investigated using equal channel angular pressing (ECAP). ECAP was conducted at room temperature adopting a die with a channel angle of 120° via route BC. Special attention was paid on the microstructure evolution and mechanical properties of the ECAP samples. Deformation twins were found in most grains after the first and second pass of ECAP. After four ECAP passes, the original grains were refined from 28 μm to about 250 nm, and the ultimate strength and microhardness were significantly enhanced to 773 MPa and 2486 MPa, respectively. Meanwhile good ductility of 16.8% elongation still remained.
2016, 45(5):1093-1099.
Abstract:
Microwave irradiation has advantages of being simple, quick and provides uniform heat. Such method was used for supporting metal oxides on ordered mesoporous carbon (OMC), which was named as NiO/C. Microwave assisted heating process involved Ni2 being reduced by glycol under alkaline surroundings. This greatly shortened supporting time and provided quantificational support when comparing with conventional impregnation method. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption, inductively coupled plasma (ICP) and cyclic voltammetry (CV) were employed to characterize the samples. Slightly reduce of pore size showed that nanoparticles were embedded on the pore wall of OMC. However, retaining ordered mesostructure and large surface area with appropriate NiO content were confirmed by XRD, TEM and nitrogen sorption. The data of ICP showed high supporting efficiency in microwave-assisted method. A great specific capacitance over 400 F?g-1 and high electrochemical stability implied favorable application prospect for this supporting method.
Microwave irradiation has advantages of being simple, quick and provides uniform heat. Such method was used for supporting metal oxides on ordered mesoporous carbon (OMC), which was named as NiO/C. Microwave assisted heating process involved Ni2 being reduced by glycol under alkaline surroundings. This greatly shortened supporting time and provided quantificational support when comparing with conventional impregnation method. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption, inductively coupled plasma (ICP) and cyclic voltammetry (CV) were employed to characterize the samples. Slightly reduce of pore size showed that nanoparticles were embedded on the pore wall of OMC. However, retaining ordered mesostructure and large surface area with appropriate NiO content were confirmed by XRD, TEM and nitrogen sorption. The data of ICP showed high supporting efficiency in microwave-assisted method. A great specific capacitance over 400 F?g-1 and high electrochemical stability implied favorable application prospect for this supporting method.
2011, 40(12):2241-2244.
Abstract:
In order to understand the adhesion failure between Ni-coating and sintered NdFeB substrate, the effect of pickling process on the adhesion strength of Ni-coating on NdFeB substrate was studied. The results reveal that the pickling leads to the formation of loose structure on NdFeB surface and the reduction of micro-hardness of NdFeB surface. The adhesion strength of Ni-coating on NdFeB substrate declines gradually with the increasing time of pickling. It can be found from the cross section morphology of stripped layer that the adhesion failure occurs in inner NdFeB substrate close to the surface, rather than in the interface between Ni-coating and NdFeB substrate.
In order to understand the adhesion failure between Ni-coating and sintered NdFeB substrate, the effect of pickling process on the adhesion strength of Ni-coating on NdFeB substrate was studied. The results reveal that the pickling leads to the formation of loose structure on NdFeB surface and the reduction of micro-hardness of NdFeB surface. The adhesion strength of Ni-coating on NdFeB substrate declines gradually with the increasing time of pickling. It can be found from the cross section morphology of stripped layer that the adhesion failure occurs in inner NdFeB substrate close to the surface, rather than in the interface between Ni-coating and NdFeB substrate.
2017, 46(1):7-11.
Abstract:
The ionic conductivity of Li3PO4 dispersed Li0.5La0.5TiO3 (LLTO) composite solid electrolyte was examined by using complex impedance analysis. The X-ray powder diffraction (XRD), scanning electron microscope (SEM) observation and relative density measurement were also performed to study the dispersion of the second phase into the LLTO electrolyte. It was found that the addition of Li3PO4 into LLTO matrix leads to a decrease of the ionic conductivity, though the composites added by the Li3PO4 particles show a high compactness. The reasons for the conductivity deterioration were clarified based on the lattice structure of LLTO, misconstrues at the grain boundary regions, and the lithium content. The variation of the lithium content and microstructures in the LLTO matrix dispersed by Li3PO4 particles are mostly responsible for the behaviors in the ionic conduction.
The ionic conductivity of Li3PO4 dispersed Li0.5La0.5TiO3 (LLTO) composite solid electrolyte was examined by using complex impedance analysis. The X-ray powder diffraction (XRD), scanning electron microscope (SEM) observation and relative density measurement were also performed to study the dispersion of the second phase into the LLTO electrolyte. It was found that the addition of Li3PO4 into LLTO matrix leads to a decrease of the ionic conductivity, though the composites added by the Li3PO4 particles show a high compactness. The reasons for the conductivity deterioration were clarified based on the lattice structure of LLTO, misconstrues at the grain boundary regions, and the lithium content. The variation of the lithium content and microstructures in the LLTO matrix dispersed by Li3PO4 particles are mostly responsible for the behaviors in the ionic conduction.
1999(4):236-239.
Abstract:
The distribution of T 1 precipitates at the subgrain boundaries and the nucleation of secondary precipitates in the alloy aluminum lithium 2090 have been studied using TEM. The results show that the aspect ratios of the T 1 phase particles which precipitate at the subgrain boundaries is similar to or even smaller than those of nearby T 1 phases, indicating limited coarsening of the T 1 phase. It is calculated that this result conforms to the Perovic criterion, i.e. that it is necessary to balance the elastic interaction energy among the T 1 precipitates in order to stabilize the distribution of the T 1 precipitates. Small T 1 precipitates always appear at the intersection between existing T 1 phases where the nucleation energy of the T 1 phase is lower
The distribution of T 1 precipitates at the subgrain boundaries and the nucleation of secondary precipitates in the alloy aluminum lithium 2090 have been studied using TEM. The results show that the aspect ratios of the T 1 phase particles which precipitate at the subgrain boundaries is similar to or even smaller than those of nearby T 1 phases, indicating limited coarsening of the T 1 phase. It is calculated that this result conforms to the Perovic criterion, i.e. that it is necessary to balance the elastic interaction energy among the T 1 precipitates in order to stabilize the distribution of the T 1 precipitates. Small T 1 precipitates always appear at the intersection between existing T 1 phases where the nucleation energy of the T 1 phase is lower
2009, 38(9):1613-1617.
Abstract:
The strengthening effects of Al-Zr-Cr-La dispersoids to Al-Mg alloys have investigated. The results show that adding Cr and La and adding Zr, Cr and La at tha same time can improve the hardness and strength and the capability to inhibit the recrystalization for the Al-Mg alloys. Comparing wih adding Cr and La, adding Zr, Cr and La at the same time has more obvious effect to inhibit the recrystalization and increase their hardness and strength
The strengthening effects of Al-Zr-Cr-La dispersoids to Al-Mg alloys have investigated. The results show that adding Cr and La and adding Zr, Cr and La at tha same time can improve the hardness and strength and the capability to inhibit the recrystalization for the Al-Mg alloys. Comparing wih adding Cr and La, adding Zr, Cr and La at the same time has more obvious effect to inhibit the recrystalization and increase their hardness and strength
2010, 39(10):1868-1874.
Abstract:
The effects of the exchange-coupling between nano-grains on effective anisotropy and coercivity of Nd-Fe-B based nanocomposite permanent magnets were discussed, and the coercivity mechanism of the magnets was also analyzed. The exchange-coupling between hard grains promotes the movement of domain walls and the reversal of magnetic moment at the applied field, which decreases the coercivity of nanocomposite magnets. Therefore, nonmagnetic grain boundary phases with suitable thickness can weaken the exchange-coupling between nano-grains of hard magnetic phase to improve the coercivity of nanocomposite permanent magnets. Besides the nucleation field and self-pining, the pining effect of nonmagnetic precipitates distributed in grains may impede the movement of the domain walls to further increase the coercivity of nanocomposite magnets.
The effects of the exchange-coupling between nano-grains on effective anisotropy and coercivity of Nd-Fe-B based nanocomposite permanent magnets were discussed, and the coercivity mechanism of the magnets was also analyzed. The exchange-coupling between hard grains promotes the movement of domain walls and the reversal of magnetic moment at the applied field, which decreases the coercivity of nanocomposite magnets. Therefore, nonmagnetic grain boundary phases with suitable thickness can weaken the exchange-coupling between nano-grains of hard magnetic phase to improve the coercivity of nanocomposite permanent magnets. Besides the nucleation field and self-pining, the pining effect of nonmagnetic precipitates distributed in grains may impede the movement of the domain walls to further increase the coercivity of nanocomposite magnets.
2011, 40(5):935-940.
Abstract:
Ag/SnO2 composite materials were prepared by reaction synthesis, and the transformation of the alloy intermediate compound to the alloy-rich region, looking for a stable transition state to generate the final phase, was elaborated from the electron-atom level. The results indicate that the activation properties of Sn are higher than Ag, and the participation of oxygen source plays a leading role to the reaction process. The free state O decomposition in the initial reactive mixture is another important way to make the oxidation reaction proceed continually and thoroughly. Finally the complete reaction path was predicted.
Ag/SnO2 composite materials were prepared by reaction synthesis, and the transformation of the alloy intermediate compound to the alloy-rich region, looking for a stable transition state to generate the final phase, was elaborated from the electron-atom level. The results indicate that the activation properties of Sn are higher than Ag, and the participation of oxygen source plays a leading role to the reaction process. The free state O decomposition in the initial reactive mixture is another important way to make the oxidation reaction proceed continually and thoroughly. Finally the complete reaction path was predicted.
2009, 38(12):2089-2092.
Abstract:
The chopping SiCf/LAS composites were prepared by the hot-pressing method. The effects of hot-pressing time and pressures on the microstructures and the dielectric properties of the composites were researched. Compared with the LAS matrix and the SiC fibre, the results of dielectric constant testing in the range of 8-12 GHz indicate that the dielectric constant real part, imaginary part and dielectric dissipation of all samples increase by 1-3 orders of magnitude, and show obvious frequency dispersion effect. Their real parts increase while their imaginary parts and dielectric dissipations decline with the increase of the hot-pressing time or pressures. The SEM fractographs show that the composite interfacial films between the fibre and the matrix are thickened with the increase of the hot-pressing time or pressures.
The chopping SiCf/LAS composites were prepared by the hot-pressing method. The effects of hot-pressing time and pressures on the microstructures and the dielectric properties of the composites were researched. Compared with the LAS matrix and the SiC fibre, the results of dielectric constant testing in the range of 8-12 GHz indicate that the dielectric constant real part, imaginary part and dielectric dissipation of all samples increase by 1-3 orders of magnitude, and show obvious frequency dispersion effect. Their real parts increase while their imaginary parts and dielectric dissipations decline with the increase of the hot-pressing time or pressures. The SEM fractographs show that the composite interfacial films between the fibre and the matrix are thickened with the increase of the hot-pressing time or pressures.
2009, 38(8):1472-1475.
Abstract:
High-Nb dual phase wrought TiAl alloys were cold-rolled under accurate control by small-pass reduction process. Results show that the deformation of the whole sample is uniform after cold rolling, and the maximum total deformation amount would be more than 20% in the case of no intermediate annealing. The microstructure of the deformed alloy still kept a dual phase structure; γ grains were elongated along rolling direction; the residual lamellar changed from the initial disordered distribution to the distribution of keeping a definite angle to rolling direction. The annealing tests reveal that different reductions, annealing temperatures and annealing time have obvious effect on the mechanical properties and structure of the cold rolled high-Nb TiAl alloy; therefore the intermediate annealing process corresponding to different reductions are also different.
High-Nb dual phase wrought TiAl alloys were cold-rolled under accurate control by small-pass reduction process. Results show that the deformation of the whole sample is uniform after cold rolling, and the maximum total deformation amount would be more than 20% in the case of no intermediate annealing. The microstructure of the deformed alloy still kept a dual phase structure; γ grains were elongated along rolling direction; the residual lamellar changed from the initial disordered distribution to the distribution of keeping a definite angle to rolling direction. The annealing tests reveal that different reductions, annealing temperatures and annealing time have obvious effect on the mechanical properties and structure of the cold rolled high-Nb TiAl alloy; therefore the intermediate annealing process corresponding to different reductions are also different.
2011, 40(3):559-564.
Abstract:
The interaction of the metallic surface or nanoparticles with nearby fluorophores broadens the applications of the metallic nanostructures in biological assays and biotechnology, and promotes the development of novel ultrabright fluorescence probes. This paper aims to introduce the mechanism of metal-enhanced fluorescence and its research progress at home and abroad. The factors influencing the efficiency of the fluorescence emission were reviewed, and the unresolved problems and the direction of development in metal-enhanced fluorescence were also present.
The interaction of the metallic surface or nanoparticles with nearby fluorophores broadens the applications of the metallic nanostructures in biological assays and biotechnology, and promotes the development of novel ultrabright fluorescence probes. This paper aims to introduce the mechanism of metal-enhanced fluorescence and its research progress at home and abroad. The factors influencing the efficiency of the fluorescence emission were reviewed, and the unresolved problems and the direction of development in metal-enhanced fluorescence were also present.
2016, 45(5):1330-1334.
Abstract:
Using ammonium metatungstate, soluble cobalt salt, and organic carbon source as the raw materials, the WC-Co composite powder was fabricated by spray conversion, calcinations and low temperature reduction-carbonization methods. The phase composition, grain size of WC, powder morphology, particle size distribution of precursor powder and composite powder were characterized. Results show that the composite powder was composed of WC and Co phases, The grain size of WC was about 60nm; the appearance of precursor powder was a kind of spherical shell structure, some of them are broken; powder morphology was not changed after calcinations; particle surface produces a large number of pore, the powder morphology was similar with precursor powder, genetic characteristics of morphology was fine; The mean grain size of composite powder was smaller than precursor powder and the particle size distribution was narrow; The mean particle size was increased with the increase of the slurry concentration, liquid feeding rate and with the decrease of centrifugal speed, but the particle size changes slightly with different inlet temperature.
Using ammonium metatungstate, soluble cobalt salt, and organic carbon source as the raw materials, the WC-Co composite powder was fabricated by spray conversion, calcinations and low temperature reduction-carbonization methods. The phase composition, grain size of WC, powder morphology, particle size distribution of precursor powder and composite powder were characterized. Results show that the composite powder was composed of WC and Co phases, The grain size of WC was about 60nm; the appearance of precursor powder was a kind of spherical shell structure, some of them are broken; powder morphology was not changed after calcinations; particle surface produces a large number of pore, the powder morphology was similar with precursor powder, genetic characteristics of morphology was fine; The mean grain size of composite powder was smaller than precursor powder and the particle size distribution was narrow; The mean particle size was increased with the increase of the slurry concentration, liquid feeding rate and with the decrease of centrifugal speed, but the particle size changes slightly with different inlet temperature.
2016, 45(12):3050-3056.
Abstract:
Disc-milling is used in manufacture, especially for difficult-to-machine material like titanium alloy, because of its strong force and high efficiency. However, the research on cutting mechanism of disc-milling technique is still lack in literature. In the present study, first, disc-milling grooving experiment was carried out to measure milling force and temperature for titanium alloy sample. After machining, surface roughness, surface topography, residual stress, microstructure and microhardness in different milling conditions were analyzed. The results showed that the surface roughness of the center on milling surface was lower than the edge; moreover, the surface roughness decreased with the increase of spindle speed, but increased with the increase of depth of cut and feed speed. The dent and crack were observed on the center and edge of milling surface, respectively. The residual compressive stress was produced on the machined surface and subsurface, and gradually reduced to zero with the increase of depth. The microstructure of lattice tensile deformation was found along feed direction under the effect of milling force, progressing from initial equiaxed structure to long flake lattice. The metallographic structure of plastic deformation zone changed with the temperature, transforming from initial equiaxed microstructure to a lamellar microstructure when the temperature was up to β-phase transition temperature. The combination of mechanical and thermal loads led to an increment in microhardness on the machined surface and subsurface.
Disc-milling is used in manufacture, especially for difficult-to-machine material like titanium alloy, because of its strong force and high efficiency. However, the research on cutting mechanism of disc-milling technique is still lack in literature. In the present study, first, disc-milling grooving experiment was carried out to measure milling force and temperature for titanium alloy sample. After machining, surface roughness, surface topography, residual stress, microstructure and microhardness in different milling conditions were analyzed. The results showed that the surface roughness of the center on milling surface was lower than the edge; moreover, the surface roughness decreased with the increase of spindle speed, but increased with the increase of depth of cut and feed speed. The dent and crack were observed on the center and edge of milling surface, respectively. The residual compressive stress was produced on the machined surface and subsurface, and gradually reduced to zero with the increase of depth. The microstructure of lattice tensile deformation was found along feed direction under the effect of milling force, progressing from initial equiaxed structure to long flake lattice. The metallographic structure of plastic deformation zone changed with the temperature, transforming from initial equiaxed microstructure to a lamellar microstructure when the temperature was up to β-phase transition temperature. The combination of mechanical and thermal loads led to an increment in microhardness on the machined surface and subsurface.
Yang Zhaozhu
,
Xue Chengshan
,
Zhuang Huizhao
,
Wang Gongtang
,
Chen Jinhua
,
Li Hong
,
Qin Lixia
,
Wang Zouping
2009, 38(3):377-379.
Abstract:
Large-scale GaN nanowires were synthesized on Si(111) substrates through ammoniating Ga2O3/V films. The as-grown products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results reveal that the grown GaN nanowires have a smooth and clean surface with diameters ranging from 20 nm to 60 nm and lengths of about several tens of micrometers. The results of HRTEM and selected-area electron diffraction (SAED) show that the nanowires are pure hexagonal GaN single crystal. The photoluminescence (PL) spectrum indicates that the GaN nanowires have good emission property. The growth mechanism is discussed briefly.
Large-scale GaN nanowires were synthesized on Si(111) substrates through ammoniating Ga2O3/V films. The as-grown products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results reveal that the grown GaN nanowires have a smooth and clean surface with diameters ranging from 20 nm to 60 nm and lengths of about several tens of micrometers. The results of HRTEM and selected-area electron diffraction (SAED) show that the nanowires are pure hexagonal GaN single crystal. The photoluminescence (PL) spectrum indicates that the GaN nanowires have good emission property. The growth mechanism is discussed briefly.
2009, 38(12):2217-2221.
Abstract:
Films with gradient pores (gradient layer) were prepared on rough-pore substrate materials by centrifugal deposition process. The relationship between the filtration performance of the composites and the particle size as well as the thickness of gradient layers was investigated. Results show the particle size of gradient layers should be less than the mean flow pore size of substrate materials so as to obtain the optimum filtration performance. With the thickness of gradient layers increasing, the permeability of the composites decreased while the filtration precision increased. There is optimum matching thickness of gradient layers for the optimum matching of the two performances, which has linear relation with the particle size of gradient layers, and the mean flow pore size of substrate materials is the intercept of the straight line.
Films with gradient pores (gradient layer) were prepared on rough-pore substrate materials by centrifugal deposition process. The relationship between the filtration performance of the composites and the particle size as well as the thickness of gradient layers was investigated. Results show the particle size of gradient layers should be less than the mean flow pore size of substrate materials so as to obtain the optimum filtration performance. With the thickness of gradient layers increasing, the permeability of the composites decreased while the filtration precision increased. There is optimum matching thickness of gradient layers for the optimum matching of the two performances, which has linear relation with the particle size of gradient layers, and the mean flow pore size of substrate materials is the intercept of the straight line.
2009, 38(3):468-472.
Abstract:
In this paper, soldered lap joint specimens were fabricated by a solder reflow process using a Sn-3.8Ag-0.7Cu-xRE (x=0, 0.1wt%, 0.25wt%, 0.5wt%) BGA solder ball on FR4 substrate parts. The effects of rare earth(RE) content and strain rate on the shear properties of soldered lap joint were investigated. The Results show that the addition of minute RE (<0.25wt%) can improve the shear strength and elongation of the lap joint. However, further increasing of RE content would degrade the shear properties of the lap joint. The shear strength and elongation of the lap joint increase with the increase of strain rate. The analysis of the microstructure and fractograph indicated that through the addition of minute RE, the microstructure of the lap joint was refined, especially the growth of intermetallic compound was inhibited, and thus the shear properties of the lap joint were improved. In addition, the observation of fractographs confirmed that the elongation of the lap joint increase with the increase of strain rate
In this paper, soldered lap joint specimens were fabricated by a solder reflow process using a Sn-3.8Ag-0.7Cu-xRE (x=0, 0.1wt%, 0.25wt%, 0.5wt%) BGA solder ball on FR4 substrate parts. The effects of rare earth(RE) content and strain rate on the shear properties of soldered lap joint were investigated. The Results show that the addition of minute RE (<0.25wt%) can improve the shear strength and elongation of the lap joint. However, further increasing of RE content would degrade the shear properties of the lap joint. The shear strength and elongation of the lap joint increase with the increase of strain rate. The analysis of the microstructure and fractograph indicated that through the addition of minute RE, the microstructure of the lap joint was refined, especially the growth of intermetallic compound was inhibited, and thus the shear properties of the lap joint were improved. In addition, the observation of fractographs confirmed that the elongation of the lap joint increase with the increase of strain rate
2010, 39(2):352-356.
Abstract:
The microstructure and mechanical properties of Al-Mg2Si alloys by equal channel angular pressing (ECAP) at 250 oC were studied. Vickers hardness and tensile testing show that the hardness, tensile strength and elongation of the alloys increase after ECAP for 4 passes. However, the hardness and tensile strength decrease after ECAP for 8 passes while the elongation increases further. SEM and TEM observations show that the original skelecton shape or the Chinese-script Mg2Si phase are obviously broken after ECAP. The more the extrusion passes, the more the fragmentated Mg2Si phase, and the more the alloys refining. The mechanism for the decrease in hardness and tensile strength of the specimen after ECAP for 8 passes compared with 4 passes was discussed.
The microstructure and mechanical properties of Al-Mg2Si alloys by equal channel angular pressing (ECAP) at 250 oC were studied. Vickers hardness and tensile testing show that the hardness, tensile strength and elongation of the alloys increase after ECAP for 4 passes. However, the hardness and tensile strength decrease after ECAP for 8 passes while the elongation increases further. SEM and TEM observations show that the original skelecton shape or the Chinese-script Mg2Si phase are obviously broken after ECAP. The more the extrusion passes, the more the fragmentated Mg2Si phase, and the more the alloys refining. The mechanism for the decrease in hardness and tensile strength of the specimen after ECAP for 8 passes compared with 4 passes was discussed.
2017, 46(3):704-710.
Abstract:
The ultrafine/nanostructured WC-10Co-4Cr composite powder was synthesized by reduction and carburization reactions, the composite powder was agglomerated to prepare the composite powder feeding that was used in spraying, then the ultrafine/nanostructured WC-10Co-4Cr coating was prepared by high velocity oxygen fuel (HVOF). The phases, elemental distribution and microstructure of the coating were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM), and then the wear resistance and corrosion resistance of the coating were tested. The results show that the main phases of the coating is WC , binding phase of amorphous structure is Co(Cr), and there is a little W2C phase of hexagonal crystal structure and W2C Co(Cr) multiphase of amorphous coexisting. The change rule of WC grain were obtained from phase boundary to eutectic area to Co area by the quantitative analysis of distribution of Co and Cr element in coating. Combined WC-10Co-4Cr composite powder and process characteristics of HVOF, explain the causes of Cr in the WC-10Co-4Cr coating distribution, and discusses the impact on the coating performance.
The ultrafine/nanostructured WC-10Co-4Cr composite powder was synthesized by reduction and carburization reactions, the composite powder was agglomerated to prepare the composite powder feeding that was used in spraying, then the ultrafine/nanostructured WC-10Co-4Cr coating was prepared by high velocity oxygen fuel (HVOF). The phases, elemental distribution and microstructure of the coating were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM), and then the wear resistance and corrosion resistance of the coating were tested. The results show that the main phases of the coating is WC , binding phase of amorphous structure is Co(Cr), and there is a little W2C phase of hexagonal crystal structure and W2C Co(Cr) multiphase of amorphous coexisting. The change rule of WC grain were obtained from phase boundary to eutectic area to Co area by the quantitative analysis of distribution of Co and Cr element in coating. Combined WC-10Co-4Cr composite powder and process characteristics of HVOF, explain the causes of Cr in the WC-10Co-4Cr coating distribution, and discusses the impact on the coating performance.
2017, 46(3):651-656.
Abstract:
The influences of B element on the microstructure and property of AlCoCrFeNiBx high entropy alloys (x denotes the atomic fraction of B element 0, 0.1, 0.25, 0.5, 0.75 and 1.0) were investigated. The AlCoCrFeNi high entropy alloy exhibit equiaxed grain morphology, then turns to dendrite structure when B content, x=0.1. The spinodal decomposition microstructure can be clearly observed in equiaxed grains. When x>0.1, both of the dendrite and the spinodal decomposition microstructure gradually disappeared, but much borides formed instead. The transformation is attributed to the high negative mixing enthalpy of Cr-B and Co-B. The microstructures of AlCoCrFeNiBx high entropy alloys changed from B2 BCC structures to B2 BCC FCC structures, finally formed B2 BCC FCC and borides mixing structures with the increased B elements. And the hardness declined from HV486.0 to HV460.7, then rose to HV615.7 as the addition of B element. The lowest hardness value is obtained when x=0.1. The compressive fracture strength shows a distinct decrease with B addition. The maximum compression strength is 2227MPa when x=0.25. But when x reached 0.75, the samples fractured during the elastic deformation due to the formation of hard and brittle borides. The coercive forces and the specific saturation magnetizations of the alloys decrease as the contents B element increase. The decreasing coercive forces show a better soft magnetic behavior.
The influences of B element on the microstructure and property of AlCoCrFeNiBx high entropy alloys (x denotes the atomic fraction of B element 0, 0.1, 0.25, 0.5, 0.75 and 1.0) were investigated. The AlCoCrFeNi high entropy alloy exhibit equiaxed grain morphology, then turns to dendrite structure when B content, x=0.1. The spinodal decomposition microstructure can be clearly observed in equiaxed grains. When x>0.1, both of the dendrite and the spinodal decomposition microstructure gradually disappeared, but much borides formed instead. The transformation is attributed to the high negative mixing enthalpy of Cr-B and Co-B. The microstructures of AlCoCrFeNiBx high entropy alloys changed from B2 BCC structures to B2 BCC FCC structures, finally formed B2 BCC FCC and borides mixing structures with the increased B elements. And the hardness declined from HV486.0 to HV460.7, then rose to HV615.7 as the addition of B element. The lowest hardness value is obtained when x=0.1. The compressive fracture strength shows a distinct decrease with B addition. The maximum compression strength is 2227MPa when x=0.25. But when x reached 0.75, the samples fractured during the elastic deformation due to the formation of hard and brittle borides. The coercive forces and the specific saturation magnetizations of the alloys decrease as the contents B element increase. The decreasing coercive forces show a better soft magnetic behavior.
2016, 45(5):1230-1234.
Abstract:
Effects of laser peening and shot peening on fatigue performance of the powder metallurgy nickel-based FGH97 superalloy were investigated. Compressive residual stresses in the surface layer were analyzed by the X-ray diffraction stress analyse tester. The rotating bending fatigue test at 650℃ was used to compare the surface enhancement effects between laser peening and shot peening. Moveover, the fatigue fracture characteristics were analyzed by scanning electron microscope. The results showed that both laser peening and shot peening can improve the fatigue property of FGH97, but laser peening had much better surface enhance effect than shot peening due to deeper compressive residual stress layer and good surface roughness, and the compressive residual stresses induced by laser peening were more stable than ones by shot peening under fatigue process at high temperature. Furthermore, the fatigue crack sources of both laser peened and shot peened speciemens initiated subsurface, while untreated at the surface.
Effects of laser peening and shot peening on fatigue performance of the powder metallurgy nickel-based FGH97 superalloy were investigated. Compressive residual stresses in the surface layer were analyzed by the X-ray diffraction stress analyse tester. The rotating bending fatigue test at 650℃ was used to compare the surface enhancement effects between laser peening and shot peening. Moveover, the fatigue fracture characteristics were analyzed by scanning electron microscope. The results showed that both laser peening and shot peening can improve the fatigue property of FGH97, but laser peening had much better surface enhance effect than shot peening due to deeper compressive residual stress layer and good surface roughness, and the compressive residual stresses induced by laser peening were more stable than ones by shot peening under fatigue process at high temperature. Furthermore, the fatigue crack sources of both laser peened and shot peened speciemens initiated subsurface, while untreated at the surface.
2009, 38(10):1765-1768.
Abstract:
FeCrAl fibrous porous materials with the porosity larger than 85% were prepared using the fiber of 20 μm in diameter as starting material. Under the ordinary sound pressure and high sound intensity conditions, the sound absorption properties of FeCrAl sintering fibrous porous materials were tested. The results indicate that the sound absorption properties of FeCrAl fibrous porous materials were increased by increasing of the porosity under ordinary sound pressure. But it was not beneficial to sound absorption under high frequency when the porosity was too high or too low. The larger the thickness was, the better the sound absorption properties of FeCrAl fibrous porous materials were. Adding the airspace can improve the sound absorption properties under low frequency. Under high sound intensity (100-140 dB), the sound absorption properties of the material would not change with the sound pressure level (SPL); effects of the parameters on the sound absorption properties were in concordance with that under ordinary sound pressure. The sound absorption coefficient of FeCrAl fibrous porous materials with 94% porosity and 20 mm thickness was up to 90% at 120 dB and in the frequency range of 2.5-6.4 kHz.
FeCrAl fibrous porous materials with the porosity larger than 85% were prepared using the fiber of 20 μm in diameter as starting material. Under the ordinary sound pressure and high sound intensity conditions, the sound absorption properties of FeCrAl sintering fibrous porous materials were tested. The results indicate that the sound absorption properties of FeCrAl fibrous porous materials were increased by increasing of the porosity under ordinary sound pressure. But it was not beneficial to sound absorption under high frequency when the porosity was too high or too low. The larger the thickness was, the better the sound absorption properties of FeCrAl fibrous porous materials were. Adding the airspace can improve the sound absorption properties under low frequency. Under high sound intensity (100-140 dB), the sound absorption properties of the material would not change with the sound pressure level (SPL); effects of the parameters on the sound absorption properties were in concordance with that under ordinary sound pressure. The sound absorption coefficient of FeCrAl fibrous porous materials with 94% porosity and 20 mm thickness was up to 90% at 120 dB and in the frequency range of 2.5-6.4 kHz.
2009, 38(3):456-459.
Abstract:
The electrochemical reduction process of Zr(Ⅳ) was studied at molybdenum electrodes in K2ZrF6-LiCl-KCl molten salt at 923 K by transient electrochemical techniques, such as cyclic voltammetry, chronopotentiometry and chronoamperometry. The experimental results show that Zr(Ⅳ) was reduced to Zr metal by a two-step mechanism corresponding to the Zr(Ⅳ)/Zr(Ⅱ) and Zr(Ⅱ)/Zr transition. The intermediate product was identified as ZrCl2 by X-ray diffraction. The chronoamperometric studies indicate that nucleation polarization existed during the electrodeposition process of zirconium at molybdenum electrode. This polarization is an instantaneous nucleation process
The electrochemical reduction process of Zr(Ⅳ) was studied at molybdenum electrodes in K2ZrF6-LiCl-KCl molten salt at 923 K by transient electrochemical techniques, such as cyclic voltammetry, chronopotentiometry and chronoamperometry. The experimental results show that Zr(Ⅳ) was reduced to Zr metal by a two-step mechanism corresponding to the Zr(Ⅳ)/Zr(Ⅱ) and Zr(Ⅱ)/Zr transition. The intermediate product was identified as ZrCl2 by X-ray diffraction. The chronoamperometric studies indicate that nucleation polarization existed during the electrodeposition process of zirconium at molybdenum electrode. This polarization is an instantaneous nucleation process
2010, 39(12):2142-2146.
Abstract:
The phase structure and electrochemical properties of La0.8-xPrxMg0.2Ni3.8 and La0.8-xPrxMg0.2Ni3.2Al0.2Co0.4 (x=0, 0.15, 0.3, 0.4) hydrogen storage alloys were investigated systematically. The structure analyses show that the alloys are mainly composed of multiphases, such as Pr5Co19 phase, Ce5Co19 phase and CaCu5 phase. The increase of Pr content in the alloys leads to an increase of the A5B19 (Pr5Co19 +Ce5Co19)-type phases; at the same time, both the lattice parameters (a, c) and the cell volume (v) for all phases are also decreased. Al element addition favors the formation of CaCu5-type phase. The electrochemical test indicates that the A5B19-type phase alloy has good electrochemical cycle stability, and the Al and Co elements can improve the electrochemical cycle stability of A5B19-type phase alloys
The phase structure and electrochemical properties of La0.8-xPrxMg0.2Ni3.8 and La0.8-xPrxMg0.2Ni3.2Al0.2Co0.4 (x=0, 0.15, 0.3, 0.4) hydrogen storage alloys were investigated systematically. The structure analyses show that the alloys are mainly composed of multiphases, such as Pr5Co19 phase, Ce5Co19 phase and CaCu5 phase. The increase of Pr content in the alloys leads to an increase of the A5B19 (Pr5Co19 +Ce5Co19)-type phases; at the same time, both the lattice parameters (a, c) and the cell volume (v) for all phases are also decreased. Al element addition favors the formation of CaCu5-type phase. The electrochemical test indicates that the A5B19-type phase alloy has good electrochemical cycle stability, and the Al and Co elements can improve the electrochemical cycle stability of A5B19-type phase alloys
2011, 40(4):665-668.
Abstract:
The microstructural evolution of coarse-grained Ni-48Al alloy during superplastic deformation at 1075 oC with initial strain rate of 1.5×10-3 s-1 was studied using EBSD (electron back-scattered diffraction) technique. The results show that before deformation, high angle grain boundaries dominate in the coarse-grained Ni-48Al alloy with few low angle grain boundaries. During the superplastic deformation, low angle grain boundaries with misorientations less than 5° occur successively. With the increase of the deformation, the misorientations of the newly-formed low angle grain boundaries increase, low angle grain boundaries with misorientations between 6o-15° are formed, and finally high angle grain boundaries with misorientations larger than 15° are formed. There exists a sort of dynamic equilibrium between the formation rate of low-angle grain boundaries and the rate of changing into higher-angle grain boundaries. The transformation from low angle grain boundaries to high angle grain boundaries makes the number of high-angle grain boundaries increase continuously and finally the grains are refined markedly.
The microstructural evolution of coarse-grained Ni-48Al alloy during superplastic deformation at 1075 oC with initial strain rate of 1.5×10-3 s-1 was studied using EBSD (electron back-scattered diffraction) technique. The results show that before deformation, high angle grain boundaries dominate in the coarse-grained Ni-48Al alloy with few low angle grain boundaries. During the superplastic deformation, low angle grain boundaries with misorientations less than 5° occur successively. With the increase of the deformation, the misorientations of the newly-formed low angle grain boundaries increase, low angle grain boundaries with misorientations between 6o-15° are formed, and finally high angle grain boundaries with misorientations larger than 15° are formed. There exists a sort of dynamic equilibrium between the formation rate of low-angle grain boundaries and the rate of changing into higher-angle grain boundaries. The transformation from low angle grain boundaries to high angle grain boundaries makes the number of high-angle grain boundaries increase continuously and finally the grains are refined markedly.
2008, 37(1):125-129.
Abstract:
对90W-7Ni-3Fe高比重合金微波烧结工艺进行了系统的研究,比较了合金在2种温度下的微波烧结与常规氢气烧结工艺的性能.结果表明:微波液相烧结比固相烧结效果好,但微波烧结试样的各项性能均低于常规烧结.微波液相烧结相对密度97.5%要比常规烧结相对密度99.2%低;前者的布氏硬度2500 MPa低于后者的2600 MPa;前者的抗拉强度694.21 MPa低于后者的776.97 MPa.1460 ℃微波固相烧结的性能明显偏低,其内部组织疏松且有大量孔洞,但其外层却相当致密,微观组织也较均匀;1480 ℃微波液相烧结的内部组织整体比较均匀,但致密化程度较低,其粘结相分布不均匀,断裂多为沿晶断裂,只有少量穿晶断裂.
对90W-7Ni-3Fe高比重合金微波烧结工艺进行了系统的研究,比较了合金在2种温度下的微波烧结与常规氢气烧结工艺的性能.结果表明:微波液相烧结比固相烧结效果好,但微波烧结试样的各项性能均低于常规烧结.微波液相烧结相对密度97.5%要比常规烧结相对密度99.2%低;前者的布氏硬度2500 MPa低于后者的2600 MPa;前者的抗拉强度694.21 MPa低于后者的776.97 MPa.1460 ℃微波固相烧结的性能明显偏低,其内部组织疏松且有大量孔洞,但其外层却相当致密,微观组织也较均匀;1480 ℃微波液相烧结的内部组织整体比较均匀,但致密化程度较低,其粘结相分布不均匀,断裂多为沿晶断裂,只有少量穿晶断裂.
2009, 38(9):1518-1525.
Abstract:
By the first-principles calculations method based on the density functional theory, H2 adsorption and dissociation properties on clean, vacancy defective and Pd atom coadsorption Mg(0001) surfaces are investigated systematically. The calculation results show that the model of H2 adsorption on clean surface is weak physisorption, and there is a high energy barrier, i.e., 1.3774 eV, when H2 dissociates into two separate H atoms. Vacancy defect not only benefits enhancing of the physisorption interaction between H2 and Mg surface, but also decreasing of the energy barrier, i.e., 1.2221 eV, of H2 dissociation to some extent. For Pd atom coadsorption Mg(0001) surface, there is a strong chemisorption interaction between Pd atom and H2, and the energy barrier, i.e., 0.2860 eV, of H2 dissociation is reduced significantly. Further analysis of electronic structures shows that the catalytic activity for H2 adsorption and dissociation on three different surfaces is closely related to the bonding electrons number of s orbital of the topmost layer metal atoms which interact directly with H2 around Fermi level
By the first-principles calculations method based on the density functional theory, H2 adsorption and dissociation properties on clean, vacancy defective and Pd atom coadsorption Mg(0001) surfaces are investigated systematically. The calculation results show that the model of H2 adsorption on clean surface is weak physisorption, and there is a high energy barrier, i.e., 1.3774 eV, when H2 dissociates into two separate H atoms. Vacancy defect not only benefits enhancing of the physisorption interaction between H2 and Mg surface, but also decreasing of the energy barrier, i.e., 1.2221 eV, of H2 dissociation to some extent. For Pd atom coadsorption Mg(0001) surface, there is a strong chemisorption interaction between Pd atom and H2, and the energy barrier, i.e., 0.2860 eV, of H2 dissociation is reduced significantly. Further analysis of electronic structures shows that the catalytic activity for H2 adsorption and dissociation on three different surfaces is closely related to the bonding electrons number of s orbital of the topmost layer metal atoms which interact directly with H2 around Fermi level
2010, 39(2):194-198.
Abstract:
Superplasticity and deformation mechanism of Mg-7.0Al-0.2Zn（AZ70）alloys without typical fine-grained structure was investigated. It is indicated that the AZ70 alloy exhibits superior superplasticity and the maximum elongation of 191.5% was obtained at 380 ℃ and 1×10-3 s-1. It is worth mentioned that high-strain-rate (＝1×10-2 s-1) superplasticity with elongation of 161.5% was achieved at 380 ℃. The mean grain sizes increase with temperature increasing and strain rate decreasing. The grain boundary sliding (GBS) is the dominant deformation mode of the superplasticity, which is verified by grains remaining equiaxial during deformation. Cavities form and grow up along grain boundary. And then the growth and connection of cavities results in the final failure. SEM morphology of the failure surface shows typical tenacity failure characteristics with quantities of uniform dimples.
Superplasticity and deformation mechanism of Mg-7.0Al-0.2Zn（AZ70）alloys without typical fine-grained structure was investigated. It is indicated that the AZ70 alloy exhibits superior superplasticity and the maximum elongation of 191.5% was obtained at 380 ℃ and 1×10-3 s-1. It is worth mentioned that high-strain-rate (＝1×10-2 s-1) superplasticity with elongation of 161.5% was achieved at 380 ℃. The mean grain sizes increase with temperature increasing and strain rate decreasing. The grain boundary sliding (GBS) is the dominant deformation mode of the superplasticity, which is verified by grains remaining equiaxial during deformation. Cavities form and grow up along grain boundary. And then the growth and connection of cavities results in the final failure. SEM morphology of the failure surface shows typical tenacity failure characteristics with quantities of uniform dimples.
2012, 41(1):54-57.
Abstract:
Ti/RuO2-TiO2-SnO2 electrode with IrO2-MnO2 interlayer was prepared via thermal decomposition. SEM, EDX, XRD and CV were employed to characterize the interlayer, and electrochemical stability was characterized by acceleration life time test. Results show that precursors are completed decomposed at 450 oC. The interlay shows fine grains, compact surface structure and low electrochemical porosity. Acceleration life time is greatly increased form 7.5 h to 995.8 h by adding interlay, much higher than the national standard of 20 h.
Ti/RuO2-TiO2-SnO2 electrode with IrO2-MnO2 interlayer was prepared via thermal decomposition. SEM, EDX, XRD and CV were employed to characterize the interlayer, and electrochemical stability was characterized by acceleration life time test. Results show that precursors are completed decomposed at 450 oC. The interlay shows fine grains, compact surface structure and low electrochemical porosity. Acceleration life time is greatly increased form 7.5 h to 995.8 h by adding interlay, much higher than the national standard of 20 h.
2009, 38(4):565-569.
Abstract:
Single-crystalline GaN nanowires have been synthesized on Si(111) substrates by magnetron sputtering through ammoniating the Ga2O3/Nb films at 900 °C in a quartz tube. The as-prepared nanowires are confirmed as single crystalline GaN with wurtzite structure by X-ray diffraction (XRD), selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). Transmission electron microscopy (TEM) shows that the GaN nanowires are straight and smooth, and possess the diameters of about 50 nm and lengths up to several microns. When excited by 325 nm helium-cadmium (He-Cd) laser light at room temperature, the GaN nanowires only have a strong ultraviolet luminescence peak located at 367 nm, owing to GaN band-edge emission. Finally, the growth mechanism of GaN nanowires is discussed briefly.
Single-crystalline GaN nanowires have been synthesized on Si(111) substrates by magnetron sputtering through ammoniating the Ga2O3/Nb films at 900 °C in a quartz tube. The as-prepared nanowires are confirmed as single crystalline GaN with wurtzite structure by X-ray diffraction (XRD), selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). Transmission electron microscopy (TEM) shows that the GaN nanowires are straight and smooth, and possess the diameters of about 50 nm and lengths up to several microns. When excited by 325 nm helium-cadmium (He-Cd) laser light at room temperature, the GaN nanowires only have a strong ultraviolet luminescence peak located at 367 nm, owing to GaN band-edge emission. Finally, the growth mechanism of GaN nanowires is discussed briefly.
92 Research on Evaporation Mechanism of Elements in TC4 Alloys during Electron Beam Cold Hearth Melting
Luo Lei
,
Yu Lanlan
,
Lei Wenguang
,
Mao Xiaonan
,
Yang Guanjun
,
Niu Rongrong
,
Zhang Yingming
,
Wang Chen
2011, 40(4):625-629.
Abstract:
A mathematical model was set up to calculate the saturated vapor pressure of components in TC4 alloys during electron beam cold hearth melting (EBCHM). The saturated vapor pressure and evaporation rate of components in TC4 alloy were calculated by this model, whose results basically agree with the experiment results. The calculation result shows that at the same temperature the saturated vapor pressure of Al is the biggest, about hundreds of times as large as others, and the evaporation loss is also the most serious. With the increase of the melt temperature, the evaporation trend increases. The evaporation loss of V is very little, which can be neglected. Moreover, electron beam cold hearth melting has the prominent effect in removing inclusions, and it can produce the slabs achieving the national standard.
A mathematical model was set up to calculate the saturated vapor pressure of components in TC4 alloys during electron beam cold hearth melting (EBCHM). The saturated vapor pressure and evaporation rate of components in TC4 alloy were calculated by this model, whose results basically agree with the experiment results. The calculation result shows that at the same temperature the saturated vapor pressure of Al is the biggest, about hundreds of times as large as others, and the evaporation loss is also the most serious. With the increase of the melt temperature, the evaporation trend increases. The evaporation loss of V is very little, which can be neglected. Moreover, electron beam cold hearth melting has the prominent effect in removing inclusions, and it can produce the slabs achieving the national standard.
2010, 39(2):309-313.
Abstract:
In order to enlarge the dimensions of titanium cladding steel plate, a new method of two main procedures was used, in which the DT4 thin slice was exploded firstly with titanium plate to assemble billet according to a symmetrical way. The effects of rolling and annealing temperatures on the shear strength of titanium cladding steel plate were investigated. The microstructures and interfacial diffusion of the cladding plates were observed or measured by optical microscope, scanning electric microscope and micro-hardness tester. The results show that the shear strength of the cladding plates is remarkably depended on the rolling and annealing temperatures, and the brittle compound amount in the interface of titanium/DT4 will increase evidently and the shear strength of titanium cladding steel plate will decrease sharply when the rolling temperature is above 882 ℃ (the α→β phase transformation temperature of titanium), or the annealing temperature is above 750 ℃. The micro-hardness peak value appears in titanium side when the annealing temperature is higher than 900 ℃ due to Fe element diffusion in titanium. Annealed within the range from 550 to 650 ℃, the shear strength will slightly increase.
In order to enlarge the dimensions of titanium cladding steel plate, a new method of two main procedures was used, in which the DT4 thin slice was exploded firstly with titanium plate to assemble billet according to a symmetrical way. The effects of rolling and annealing temperatures on the shear strength of titanium cladding steel plate were investigated. The microstructures and interfacial diffusion of the cladding plates were observed or measured by optical microscope, scanning electric microscope and micro-hardness tester. The results show that the shear strength of the cladding plates is remarkably depended on the rolling and annealing temperatures, and the brittle compound amount in the interface of titanium/DT4 will increase evidently and the shear strength of titanium cladding steel plate will decrease sharply when the rolling temperature is above 882 ℃ (the α→β phase transformation temperature of titanium), or the annealing temperature is above 750 ℃. The micro-hardness peak value appears in titanium side when the annealing temperature is higher than 900 ℃ due to Fe element diffusion in titanium. Annealed within the range from 550 to 650 ℃, the shear strength will slightly increase.
2015, 44(5):1041-1045.
Abstract:
Impulse pressuring diffusion bonding of commercially pure titanium to 1Cr18Ni9 stainless steel was carried out using a copper interlayer in an attempt to reduce the bonding time and alleviate the detrimental effect of interfacial reaction products on bonding strength. Successful bonding has been achieved at 850 °C under a pulsed pressure of 8~20 MPa within a duration of only 120~180 s, which is notably shortened in comparison with conventional diffusion bonding. Microstructure characterization revealed that a sequence of Ti-Cu intermetallic compounds were formed at the Ti/Cu interface and the Cu/stainless steel interface was characterized by the presence of solid solution of Cu in γ Fe without any interfacial reaction products. Maximum bonding strength of 346 MPa was obtained when the joint was bonded for 120 s. Upon tensile loading, the joints fractured along the Ti/Cu interfacial reaction layer in a brittle cleavage manner, indicating that the impulse pressuring diffusion bonding can alleviate the harmful influence of interfacial intermetallic compounds on joint performances to a certain extent, but it is infeasible in completely eliminating the negative effect of the brittle intermetallic compounds.
Impulse pressuring diffusion bonding of commercially pure titanium to 1Cr18Ni9 stainless steel was carried out using a copper interlayer in an attempt to reduce the bonding time and alleviate the detrimental effect of interfacial reaction products on bonding strength. Successful bonding has been achieved at 850 °C under a pulsed pressure of 8~20 MPa within a duration of only 120~180 s, which is notably shortened in comparison with conventional diffusion bonding. Microstructure characterization revealed that a sequence of Ti-Cu intermetallic compounds were formed at the Ti/Cu interface and the Cu/stainless steel interface was characterized by the presence of solid solution of Cu in γ Fe without any interfacial reaction products. Maximum bonding strength of 346 MPa was obtained when the joint was bonded for 120 s. Upon tensile loading, the joints fractured along the Ti/Cu interfacial reaction layer in a brittle cleavage manner, indicating that the impulse pressuring diffusion bonding can alleviate the harmful influence of interfacial intermetallic compounds on joint performances to a certain extent, but it is infeasible in completely eliminating the negative effect of the brittle intermetallic compounds.
2010, 39(2):333-337.
Abstract:
Co-Al co-doped cathode material LiNi0.8Co0.2-xAlxO2 (0≤x≤0.15) was directly synthesized without artificial grinding and washing by a eutectic molten-salt mixture (0.38LiOH-0.62LiNO3) method. According to this method, the eutectic molten-salt mixture was self-mixed with high tap density precursor Ni0.8Co0.2-xAlx(OH)2 thoroughly at low temperature and then sintered at a certain temperature. The tap-density of LiNi0.8Co0.15Al0.05O2 obtained is 2.97 g·cm-3. According to XRD and SEM, these LiNi0.8Co0.2-x AlxO2 materials have an order α-NaFeO2 layer structure and regular morphology. The charge-discharge tests show that the LiNi0.8Co0.15Al0.05O2 has an initial discharge capacity as high as 167.5 mAh·g-1 and excellent capacity retention in the range from 3.0 V to 4.3 V at a specific current of 0.2 C.
Co-Al co-doped cathode material LiNi0.8Co0.2-xAlxO2 (0≤x≤0.15) was directly synthesized without artificial grinding and washing by a eutectic molten-salt mixture (0.38LiOH-0.62LiNO3) method. According to this method, the eutectic molten-salt mixture was self-mixed with high tap density precursor Ni0.8Co0.2-xAlx(OH)2 thoroughly at low temperature and then sintered at a certain temperature. The tap-density of LiNi0.8Co0.15Al0.05O2 obtained is 2.97 g·cm-3. According to XRD and SEM, these LiNi0.8Co0.2-x AlxO2 materials have an order α-NaFeO2 layer structure and regular morphology. The charge-discharge tests show that the LiNi0.8Co0.15Al0.05O2 has an initial discharge capacity as high as 167.5 mAh·g-1 and excellent capacity retention in the range from 3.0 V to 4.3 V at a specific current of 0.2 C.
2010, 39(2):204-208.
Abstract:
Based on ab-initio principle and pseudo-potential plain wave function combined with density function theory, crystal lattice dynamical characteristics and thermodynamical functions of V, VH2, VD2 and VT2 were calculated. The thermodynamical isotope effect was analyzed based on those calculated data. Calculation results show that both difference of vibration frequency of atoms in VQ2 (Q=H, D and T) and difference of oscillation frequency of hydrogen isotopes are mainly responsible for the hydrogen isotope effect. The standard Gibbs free energy change of the absorption reaction rises from –50 kJ/mol to 140 kJ/mol with the temperature increasing from 10 K to 1000 K. The equilibrium pressure climbs drastically when temperature is higher than room temperature. Within the whole temperature range, only inverse hydrogen isotope effect is found
Based on ab-initio principle and pseudo-potential plain wave function combined with density function theory, crystal lattice dynamical characteristics and thermodynamical functions of V, VH2, VD2 and VT2 were calculated. The thermodynamical isotope effect was analyzed based on those calculated data. Calculation results show that both difference of vibration frequency of atoms in VQ2 (Q=H, D and T) and difference of oscillation frequency of hydrogen isotopes are mainly responsible for the hydrogen isotope effect. The standard Gibbs free energy change of the absorption reaction rises from –50 kJ/mol to 140 kJ/mol with the temperature increasing from 10 K to 1000 K. The equilibrium pressure climbs drastically when temperature is higher than room temperature. Within the whole temperature range, only inverse hydrogen isotope effect is found
2017, 46(3):612-616.
Abstract:
In order to solve the wear repair problem of large steam turbine rotor shaft journal, the material of steam turbine rotor shaft as substrate and the self-made special laser cladding remanufacturing powder as experimental material, the experiments were carried out by laser cladding remanufacturing method based on laser cladding remanufacturing system with coaxial powder feeder. Focusing on effect of different width of laser cladding layers on total indicated runout (TIR) of steam turbine rotor, the experiment research and mechanism simulation verification were performed, and the influence mechanism of different factors were analyzed. The results show that the data results of total indicated runout are closely related to probe diameter and laser cladding layer width. The width of cladding layer determines the turbine rotor surface magnetic, eddy current density and magnetic flux density distribution. Due to the interference of matrix magnetic field and eddy current density of surface, the magnetic flux density suddenly changes in the laser cladding layer edge when the laser cladding layer width is less than 8mm.The measurement results are too large caused by the comprehensive effect of substrate and laser cladding layer. According to the numerical simulation of magnetic flux density distribution of measured metal body surface, the critical value of laser cladding width is 9.82mm.
In order to solve the wear repair problem of large steam turbine rotor shaft journal, the material of steam turbine rotor shaft as substrate and the self-made special laser cladding remanufacturing powder as experimental material, the experiments were carried out by laser cladding remanufacturing method based on laser cladding remanufacturing system with coaxial powder feeder. Focusing on effect of different width of laser cladding layers on total indicated runout (TIR) of steam turbine rotor, the experiment research and mechanism simulation verification were performed, and the influence mechanism of different factors were analyzed. The results show that the data results of total indicated runout are closely related to probe diameter and laser cladding layer width. The width of cladding layer determines the turbine rotor surface magnetic, eddy current density and magnetic flux density distribution. Due to the interference of matrix magnetic field and eddy current density of surface, the magnetic flux density suddenly changes in the laser cladding layer edge when the laser cladding layer width is less than 8mm.The measurement results are too large caused by the comprehensive effect of substrate and laser cladding layer. According to the numerical simulation of magnetic flux density distribution of measured metal body surface, the critical value of laser cladding width is 9.82mm.
2017, 46(7):1821-1826.
Abstract:
In this research, the process of hydrodynamic deep drawing of Al2198 was investigated by using finite element simulation experimental works. And the effects of die cavity pressure, blank holder gap and pre-bulging pressure on the forming process and the thickness distribution were analyzed. The research indicated that the pressure inside the liquid chamber and the blank holder gap or blank holder force were the main factors affecting hydrodynamic deep drawing process. And appropriate pre-bulging pressure was beneficial to form a good quality parts with a relatively uniform wall thickness.
In this research, the process of hydrodynamic deep drawing of Al2198 was investigated by using finite element simulation experimental works. And the effects of die cavity pressure, blank holder gap and pre-bulging pressure on the forming process and the thickness distribution were analyzed. The research indicated that the pressure inside the liquid chamber and the blank holder gap or blank holder force were the main factors affecting hydrodynamic deep drawing process. And appropriate pre-bulging pressure was beneficial to form a good quality parts with a relatively uniform wall thickness.
2016, 45(12):3037-3042.
Abstract:
The Ca0.8Sr0.2TiO3 ceramics with different amounts of glass additions were successfully prepared by liquid phase sintering and used as dielectric barriers in a cylindrical dielectric barrier discharge reactor to decompose carbon dioxide at atmospheric pressure. It is found that the surface resistivity increases with increasing glass content. While the dielectric constant does not change obviously with the increase of the glass content in the investigated temperature range. The scanning electron microscope observations indicated that both the grain size and the thickness of intergranular glassy phases increase with the increase of the glass content. More importantly, the conversion rate and conversion efficiency of carbon dioxide improves with the increase of glass content in the ceramics. Furthermore, a combined discharge analysis and dielectric characterization are modeled with a Malter effect approach. From this model, it is possible to interpret the relationship between the conversion characteristics and the glass content in the ceramic samples.
The Ca0.8Sr0.2TiO3 ceramics with different amounts of glass additions were successfully prepared by liquid phase sintering and used as dielectric barriers in a cylindrical dielectric barrier discharge reactor to decompose carbon dioxide at atmospheric pressure. It is found that the surface resistivity increases with increasing glass content. While the dielectric constant does not change obviously with the increase of the glass content in the investigated temperature range. The scanning electron microscope observations indicated that both the grain size and the thickness of intergranular glassy phases increase with the increase of the glass content. More importantly, the conversion rate and conversion efficiency of carbon dioxide improves with the increase of glass content in the ceramics. Furthermore, a combined discharge analysis and dielectric characterization are modeled with a Malter effect approach. From this model, it is possible to interpret the relationship between the conversion characteristics and the glass content in the ceramic samples.
2017, 46(3):634-639.
Abstract:
This paper analyzed the microstructure of Ti6Al4V titanium alloy after different heat treatments. The tensile experiment and instrumented impact test were done. It was studied that the microstructure, mechanical properties and impact toughness of Ti6Al4V titanium alloy were affected by the solution and aging treatment. The relationship among the microstructure, impact fracture characteristic and mechanical properties was analyzed by metallurgical mi-croscope and environment scanning electron microscope (ESEM). The results showed that the yield strength and ul-timate tensile strength were improved remarkably. The ductile increased firstly, then it decreased. The good compre-hensive properties can be gotten when the Ti6Al4V titanium alloy was treated in the condition of 960 ℃×1h WQ and 500 ℃×4h AC. The σ0.2 is 1050 MPa. The σb is 1120 MPa and Ak is 46.22 J. The microstructure of the tita-nium alloy after solution and aging treatment was consisted of the β matrix and the precipitation of the α-phase. The lamellar β-phase and the α-phase structure of the small needle plexiform can enhance comprehensive properties.
This paper analyzed the microstructure of Ti6Al4V titanium alloy after different heat treatments. The tensile experiment and instrumented impact test were done. It was studied that the microstructure, mechanical properties and impact toughness of Ti6Al4V titanium alloy were affected by the solution and aging treatment. The relationship among the microstructure, impact fracture characteristic and mechanical properties was analyzed by metallurgical mi-croscope and environment scanning electron microscope (ESEM). The results showed that the yield strength and ul-timate tensile strength were improved remarkably. The ductile increased firstly, then it decreased. The good compre-hensive properties can be gotten when the Ti6Al4V titanium alloy was treated in the condition of 960 ℃×1h WQ and 500 ℃×4h AC. The σ0.2 is 1050 MPa. The σb is 1120 MPa and Ak is 46.22 J. The microstructure of the tita-nium alloy after solution and aging treatment was consisted of the β matrix and the precipitation of the α-phase. The lamellar β-phase and the α-phase structure of the small needle plexiform can enhance comprehensive properties.
