Volume 45,Issue 12,2016 Table of Contents
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.
2016, 45(12):3043-3049.
Abstract:
The influence of aging temperature (200 to 800 °C) on grain boundary segregations in a Ni-20Cr-18W-1Mo superalloy was investigated by scanning electronic microscope (SEM), transmission electron microscopy (TEM), electron microprobe analyzer (EMPA) and mechanical testing machine. Results indicate that the grain boundary segregation critical times of sulfur and phosphorus decrease with increasing aging temperature. Increasing of aging temperature has a conspicuous effect on the concentration distribution between the grain boundary and grain core. Grain boundary concentrations of sulfur and phosphorus increase with increment of testing temperature until a peak value obtained at 650 and 400 °C, respectively, which is the essential reason to the declined mechanical properties from 200 to 600 °C.
The influence of aging temperature (200 to 800 °C) on grain boundary segregations in a Ni-20Cr-18W-1Mo superalloy was investigated by scanning electronic microscope (SEM), transmission electron microscopy (TEM), electron microprobe analyzer (EMPA) and mechanical testing machine. Results indicate that the grain boundary segregation critical times of sulfur and phosphorus decrease with increasing aging temperature. Increasing of aging temperature has a conspicuous effect on the concentration distribution between the grain boundary and grain core. Grain boundary concentrations of sulfur and phosphorus increase with increment of testing temperature until a peak value obtained at 650 and 400 °C, respectively, which is the essential reason to the declined mechanical properties from 200 to 600 °C.
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.
2016, 45(12):3057-3061.
Abstract:
A TiAlN coating on the surface of a WC-8Co cemented carbide matrix with thicknesses ranging from 2.5 to 3.5 μm and different ratios of TiAl composition was manufactured by means of magnetron sputtering. The carrying capacity and tribological properties of the coating were investigated on a friction-wear testing machine; the microstructure of the coating was observed by using scanning electron microscopy. The tribiological properties of TiAlN coatings of different composition and thickness were evaluated through the friction coefficient and the evolution of microstructure. The results show that when the coating thickness increases, the friction coefficient decreases, and the coating will not easily wear out, suggesting that it is beneficial to improve the wear resistance of a coating by increasing its thickness in a certain range. If the composition of the coating changes, its friction performance will vary due to the different effects of Ti and Al. is 50:50, the wear resistance of the coating is best.
A TiAlN coating on the surface of a WC-8Co cemented carbide matrix with thicknesses ranging from 2.5 to 3.5 μm and different ratios of TiAl composition was manufactured by means of magnetron sputtering. The carrying capacity and tribological properties of the coating were investigated on a friction-wear testing machine; the microstructure of the coating was observed by using scanning electron microscopy. The tribiological properties of TiAlN coatings of different composition and thickness were evaluated through the friction coefficient and the evolution of microstructure. The results show that when the coating thickness increases, the friction coefficient decreases, and the coating will not easily wear out, suggesting that it is beneficial to improve the wear resistance of a coating by increasing its thickness in a certain range. If the composition of the coating changes, its friction performance will vary due to the different effects of Ti and Al. is 50:50, the wear resistance of the coating is best.
Sui Yanwei
,
Feng Kun
,
Cheng Cheng
,
Qi Jiqiu
,
He Yezeng
,
Wei Fuxiang
,
Meng Qingkun
,
Sun Zhi
,
Shen Chengjin
2016, 45(12):3062-3067.
Abstract:
The effect of Al2O3, Y2O3 and ZrO2 coating materials to the Ti-48Al alloys on the metal-coating interface, alloy chemical composition and microstructure is evaluated by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction analysis, respectively. Microhardness variation from the surface to the inside of the samples was compared. The results indicate that inordinate interaction occurred at the interface between the coating and the melt. The crucible layer was found to suffer chemical dissolution and some physical erosion by the molten alloy and the extent of that dissolution, depend partly on the coating material. Additionally, The thermodynamics of the TiAl/Oxide reactions have been studied, and the main mechanism responsible for the contamination of the directional solidification samples is diffusion controlled dissolution of the coatings in the melt which leads to an increase of oxygen content in the matrix.
The effect of Al2O3, Y2O3 and ZrO2 coating materials to the Ti-48Al alloys on the metal-coating interface, alloy chemical composition and microstructure is evaluated by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction analysis, respectively. Microhardness variation from the surface to the inside of the samples was compared. The results indicate that inordinate interaction occurred at the interface between the coating and the melt. The crucible layer was found to suffer chemical dissolution and some physical erosion by the molten alloy and the extent of that dissolution, depend partly on the coating material. Additionally, The thermodynamics of the TiAl/Oxide reactions have been studied, and the main mechanism responsible for the contamination of the directional solidification samples is diffusion controlled dissolution of the coatings in the melt which leads to an increase of oxygen content in the matrix.
2016, 45(12):3068-3073.
Abstract:
In this paper, high Mg addition (2wt%, 4wt%, 6wt%) to AlSi7 alloy is researched. The results show that Mg can react with Al2O3 and Si element, the MgAl2O4 phase which has a good wettability with Al melt and Mg2Si phase are formed, both of them can uniformly distribute in the alloy and induce a particle based stabilization mechanism, which can significantly reduce the negative impact of gravity drainage and capillarity. High Mg content can also change the pores formation in early stage, pores nucleate in a pool of liquid and grow in a fairly spherical way, so high expansion rate and good pore structures can be obtained. The disadvantage of high Mg content is the decrease of surface tension which makes pores easy to bust. A good trade-off between the beneficial and adverse effects of Mg content for AlSi7 based alloy is 4wt%.
In this paper, high Mg addition (2wt%, 4wt%, 6wt%) to AlSi7 alloy is researched. The results show that Mg can react with Al2O3 and Si element, the MgAl2O4 phase which has a good wettability with Al melt and Mg2Si phase are formed, both of them can uniformly distribute in the alloy and induce a particle based stabilization mechanism, which can significantly reduce the negative impact of gravity drainage and capillarity. High Mg content can also change the pores formation in early stage, pores nucleate in a pool of liquid and grow in a fairly spherical way, so high expansion rate and good pore structures can be obtained. The disadvantage of high Mg content is the decrease of surface tension which makes pores easy to bust. A good trade-off between the beneficial and adverse effects of Mg content for AlSi7 based alloy is 4wt%.
2016, 45(12):3074-3079.
Abstract:
Li-B alloys have excellent potential as a battery anode material, but difficulties associated with their preparation have limited commercial application. This paper describes novel preparation techniques that allow the production of 300g quantities via improvements in several aspects of the synthesis process, including atmospheric control, temperature, cooling, and stirring practices. The alloy prepared using procedures identified in this study was uniform and porosity-free. The discharge performance of the alloy anodes prepared in this study are presented.
Li-B alloys have excellent potential as a battery anode material, but difficulties associated with their preparation have limited commercial application. This paper describes novel preparation techniques that allow the production of 300g quantities via improvements in several aspects of the synthesis process, including atmospheric control, temperature, cooling, and stirring practices. The alloy prepared using procedures identified in this study was uniform and porosity-free. The discharge performance of the alloy anodes prepared in this study are presented.
2016, 45(12):3080-3084.
Abstract:
In this paper, TiN coatings are prepared on the GCr15 substrate by the cathode arc, magnetron sputtering and their composite methods. The coatings are characterized by Scanning electron microscope (SEM), XRD spectroscopy， microscratch test, friction and wear test, and the effects of different preparation methods on the structure and mechanical properties of the coatings are compared. The results show that the coating prepared by composite arc and magnetron technique possesses better comprehensive properties such as a smooth surface, high cohesion and hardness ,so wear rate is lower.
In this paper, TiN coatings are prepared on the GCr15 substrate by the cathode arc, magnetron sputtering and their composite methods. The coatings are characterized by Scanning electron microscope (SEM), XRD spectroscopy， microscratch test, friction and wear test, and the effects of different preparation methods on the structure and mechanical properties of the coatings are compared. The results show that the coating prepared by composite arc and magnetron technique possesses better comprehensive properties such as a smooth surface, high cohesion and hardness ,so wear rate is lower.
2016, 45(12):3086-3088.
Abstract:
The present work examines the influence of heat treatment on the microstructure related to the interfacial reaction and corrosion behavior of SiCp/Al-6%Mg composites prepared by using a pressureless infiltration technique. The experimental results show the occurrence of the precipitates of Si, MgA12O4 and Mg2Si as a result of the interfacial reaction between the SiC particle and matrix of the composites during heat treatment. The precipitates contents(f) of composites are correlated with T1, T4, T6 and annealing heat treatment, following the order of fT1< fT4< fT6annealing. The precipitates located near SiC particles are responsible to pitting corrosion as a degradation mechanism of the composites. The heat treatments carried out on the composites present a significant influence on the corrosion rate (jcorr). The correlation between jcorr and heat treatment present the characteristics of jcorr-ann> jcorr-T6> jcorr-T4> jcorr-T1, which may be attributed to the the interfacial reaction precipitates of the composites during heat treatment.
The present work examines the influence of heat treatment on the microstructure related to the interfacial reaction and corrosion behavior of SiCp/Al-6%Mg composites prepared by using a pressureless infiltration technique. The experimental results show the occurrence of the precipitates of Si, MgA12O4 and Mg2Si as a result of the interfacial reaction between the SiC particle and matrix of the composites during heat treatment. The precipitates contents(f) of composites are correlated with T1, T4, T6 and annealing heat treatment, following the order of fT1< fT4< fT6
2016, 45(12):3089-3094.
Abstract:
Tungsten was subjected to severe plastic deformation at 440°C using high pressure torsion (HPT) with an improved die-set. Microhardness measurements suggest an appreciable ductility level in tungsten after HPT with Vickers microhardness as high as ~1150 HV. Differential scanning calorimetry (DSC) analyses showed that samples that developed less strain had a higher recrystallisation temperature (greater than 1450°C) than samples that developed more strain (~800°C). X-ray diffraction analyses indicate increases in lattice strain of up to 0.35%, lattice parameter up to 0.3177 nm and dislocation density up to 2.4 × 1015 m-2. The current study introduces the improved HPT process as an effective route for the production of ultrahigh strength W with significant ductility and specified thermostability.
Tungsten was subjected to severe plastic deformation at 440°C using high pressure torsion (HPT) with an improved die-set. Microhardness measurements suggest an appreciable ductility level in tungsten after HPT with Vickers microhardness as high as ~1150 HV. Differential scanning calorimetry (DSC) analyses showed that samples that developed less strain had a higher recrystallisation temperature (greater than 1450°C) than samples that developed more strain (~800°C). X-ray diffraction analyses indicate increases in lattice strain of up to 0.35%, lattice parameter up to 0.3177 nm and dislocation density up to 2.4 × 1015 m-2. The current study introduces the improved HPT process as an effective route for the production of ultrahigh strength W with significant ductility and specified thermostability.
2016, 45(12):3095-3098.
Abstract:
In order to improve the sintering characteristics of the low-temperature sintered M-type hexagonal strontium ferrites (SrFe12O19) prepared by solid phase method, the Bi2O3 additive was used as sintering aid, and the crystal structure, electrical properties, and magnetic properties of the ferrites were investigated. The results show that the single phase structural SrFe12O19 ferrites can be obtained even with a low sintering temperature of 900 癈. The Bi2O3 additive is found to possess a significant effect on the electrical properties and magnetic properties for the ferrites sintered at low temperatures, typically leading to enhanced resistivity ρ, saturation magnetization Ms, intrinsic coercivity Hci, and magnetic anisotropy field Ha. It is suggested that the low-temperature sintered SrFe12O19 ferrites with ρ of 0.42?08 Ω?cm, Ms of 285.6 kA?m-1, Hci of 347.3 kA?m-1, and Ha of 1546.6 kA?m-1 provide an important potential application in nonreciprocal LTCC (low temperature co-fired ceramics) ferrite devices.
In order to improve the sintering characteristics of the low-temperature sintered M-type hexagonal strontium ferrites (SrFe12O19) prepared by solid phase method, the Bi2O3 additive was used as sintering aid, and the crystal structure, electrical properties, and magnetic properties of the ferrites were investigated. The results show that the single phase structural SrFe12O19 ferrites can be obtained even with a low sintering temperature of 900 癈. The Bi2O3 additive is found to possess a significant effect on the electrical properties and magnetic properties for the ferrites sintered at low temperatures, typically leading to enhanced resistivity ρ, saturation magnetization Ms, intrinsic coercivity Hci, and magnetic anisotropy field Ha. It is suggested that the low-temperature sintered SrFe12O19 ferrites with ρ of 0.42?08 Ω?cm, Ms of 285.6 kA?m-1, Hci of 347.3 kA?m-1, and Ha of 1546.6 kA?m-1 provide an important potential application in nonreciprocal LTCC (low temperature co-fired ceramics) ferrite devices.
2016, 45(12):3099-3103.
Abstract:
Spherical cobalt particles with special morphology were successfully prepared on a large scale through a simple and low-cost liquid reduction method. The morphology, crystal structure, static magnetic properties and electromagnetic behavior of the cobalt particles were measured by SEM、XRD、VSM and vector network analyzer. The results show that saturation magnetization of 123 emu/g was obtained, less than that of hcp-Co single crystals, and the coercivity was 176 Oe, larger than that of bulk cobalt crystal. Furthermore, dual-nonlinear dielectric resonances were observed at 9.8 GHz and 15 GHz. The real part of permeability decreases with the frequency increasing, presenting excellent frequency dispersion property. Meanwhile, the imaginary part of permeability revealed a wide resonance peak over microwave frequency range. According to transmit-line theory, the reflection loss (RL) was predicted through the permittivity and permeability for a given frequency and absorber thickness. A maximum reflection loss of -13.2 dB was achieved at 12.4 GHz with a thickness of 5.5 mm, and the effective absorption bandwidth (≤ -10 dB) was 1.6 GHz, indicating the as-prepared cobalt particles have potential application as candidate for microwave absorption.
Spherical cobalt particles with special morphology were successfully prepared on a large scale through a simple and low-cost liquid reduction method. The morphology, crystal structure, static magnetic properties and electromagnetic behavior of the cobalt particles were measured by SEM、XRD、VSM and vector network analyzer. The results show that saturation magnetization of 123 emu/g was obtained, less than that of hcp-Co single crystals, and the coercivity was 176 Oe, larger than that of bulk cobalt crystal. Furthermore, dual-nonlinear dielectric resonances were observed at 9.8 GHz and 15 GHz. The real part of permeability decreases with the frequency increasing, presenting excellent frequency dispersion property. Meanwhile, the imaginary part of permeability revealed a wide resonance peak over microwave frequency range. According to transmit-line theory, the reflection loss (RL) was predicted through the permittivity and permeability for a given frequency and absorber thickness. A maximum reflection loss of -13.2 dB was achieved at 12.4 GHz with a thickness of 5.5 mm, and the effective absorption bandwidth (≤ -10 dB) was 1.6 GHz, indicating the as-prepared cobalt particles have potential application as candidate for microwave absorption.
2016, 45(12):3104-3107.
Abstract:
The Ti6Al4V titanium matrix composite added with (0.36, 0.72, 1.45wt. %) La and (0.17, 0.34, 0.68wt. %) B, were successfully synthesized using common casting and hot forging technology. The microstructural characteristic and tensile properties of the heat-treated materials were investigated, with purticular emphasis on the effect of trace reinforcements. The phase analysis was identified by XRD. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to observe the microstructure. Both room temperature and high temperature tensile properties were tested. The results showed that the addition of La and B plays an important role in the microstructure and mechanical properties of titanium matrix composite, tensile strength can be increased 148MPa, which can strengthen the matrix metal seriously.
The Ti6Al4V titanium matrix composite added with (0.36, 0.72, 1.45wt. %) La and (0.17, 0.34, 0.68wt. %) B, were successfully synthesized using common casting and hot forging technology. The microstructural characteristic and tensile properties of the heat-treated materials were investigated, with purticular emphasis on the effect of trace reinforcements. The phase analysis was identified by XRD. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to observe the microstructure. Both room temperature and high temperature tensile properties were tested. The results showed that the addition of La and B plays an important role in the microstructure and mechanical properties of titanium matrix composite, tensile strength can be increased 148MPa, which can strengthen the matrix metal seriously.
2016, 45(12):3108-3111.
Abstract:
Galvanostatic electrochemical processes were used to electrodeposit Bi-Te binary thin films. Single-phased Bi2Te3 and Bi4Te3 films were synthesized in turn on the same electrolyte. Bi2Te3 thin film is composed of regular nanorods with the length up to 100 nm and average width of 10 nm, which exhibited large specific areas and would be beneficial to the application as thermoelectric materials. And the Bi4Te3 thin film is composed of nanoparticles which assembled greatly into irregular polyhedrons. The results of this manuscript proved that by changing the deposition parameters, it is possible to tune the phase composition and morphology of Bi-Te binary thin films.
Galvanostatic electrochemical processes were used to electrodeposit Bi-Te binary thin films. Single-phased Bi2Te3 and Bi4Te3 films were synthesized in turn on the same electrolyte. Bi2Te3 thin film is composed of regular nanorods with the length up to 100 nm and average width of 10 nm, which exhibited large specific areas and would be beneficial to the application as thermoelectric materials. And the Bi4Te3 thin film is composed of nanoparticles which assembled greatly into irregular polyhedrons. The results of this manuscript proved that by changing the deposition parameters, it is possible to tune the phase composition and morphology of Bi-Te binary thin films.
Ping HU
,
Lu KANG
,
Jun YANG
,
Fan YANG
,
Kuai-she WANG
,
Jinjing DU
,
Zhanlin YANG
,
Weicheng CAO
,
Dongxin LIU
2016, 45(12):3112-3114.
Abstract:
In the present work, the Fe nanoparticles were synthesized via a novel method one-step reduction method. The excessive citric acid helps to obtain pure and high crystallinity α-Fe and the appropriate temperature (at 620 oC). The Fe nanoparticles were carefully characterized by the X-ray diffraction, transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The morphological characterization indicates that the Fe nanoparticles present spherical shape with diameter of 30 nm. The magnetization hysteresis loops reveal the high saturation magnetization (Ms=198.97 emu/g) and the good ferromagnetic behavior of the magnetic materials. The one-step reduction method for nanoparticles synthesis has the advantages of controllable, short process, large-scale production, and will be an important method of producing nanoparticles.
In the present work, the Fe nanoparticles were synthesized via a novel method one-step reduction method. The excessive citric acid helps to obtain pure and high crystallinity α-Fe and the appropriate temperature (at 620 oC). The Fe nanoparticles were carefully characterized by the X-ray diffraction, transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The morphological characterization indicates that the Fe nanoparticles present spherical shape with diameter of 30 nm. The magnetization hysteresis loops reveal the high saturation magnetization (Ms=198.97 emu/g) and the good ferromagnetic behavior of the magnetic materials. The one-step reduction method for nanoparticles synthesis has the advantages of controllable, short process, large-scale production, and will be an important method of producing nanoparticles.
2016, 45(12):3115-3120.
Abstract:
Fe18Ni23Co25Cr21Mo8WNb3C2 superalloy powders were synthesized via atomization method, and phase composition, morphology and thermal stability of composite powders were respectively characterized. Based on the above analysis, atomized alloy powders were fabricated by vacuum hot-pressed sintering and further second sintering. The sintering Fe-Ni-Co-based superalloy mainly consists of austenite phase and M6C carbide phase, which was a strengthening phase. Experiment results indicate that superalloy have uniform structure, high tensile strength and low elongation after vacuum hot-pressed sintering. Further second sintering, microstructure of superalloy become more homogeneous, the tensile strength decreases slightly and the elongation rate significantly increases.
Fe18Ni23Co25Cr21Mo8WNb3C2 superalloy powders were synthesized via atomization method, and phase composition, morphology and thermal stability of composite powders were respectively characterized. Based on the above analysis, atomized alloy powders were fabricated by vacuum hot-pressed sintering and further second sintering. The sintering Fe-Ni-Co-based superalloy mainly consists of austenite phase and M6C carbide phase, which was a strengthening phase. Experiment results indicate that superalloy have uniform structure, high tensile strength and low elongation after vacuum hot-pressed sintering. Further second sintering, microstructure of superalloy become more homogeneous, the tensile strength decreases slightly and the elongation rate significantly increases.
2016, 45(12):3121-3127.
Abstract:
In order to avoid the catalytic cokes forming, the TiN and TiO2 coating is directly deposited on the surface of the 310S stainless steel flake with the diameter of 10?10?0.9 mm by using atmospheric pressure chemical vapor deposition method. The deposition temperature is 850 ℃ for TiN and TiO2, respectively, and the deposition time is 2.5 h. The morphologies and structures of the coatings were analyzed by SEM, EDS and XRD, the results show that the TiN and TiO2 coating is continuous, close-packed and homogeneous; the titanium nitride in the coating had cub phase, Ti and N atomic ratio in the titanium nitride coating is 1:1, and the titanium oxide in the coating is the Ti2O3~Ti3O5 stoichiometrically. An atmospheric pressure cracking system was set up for evaluating the anti-coking property of TiN and TiO2 coating with n-hexane, cyclohexane, benzene and RP-3 as feedstock. The results show that TiN and TiO2 coating exhibit an excellent anti-coking performance, the anti-coking ratio of TiN coating for n-hexane, cyclohexane, benzene and RP-3 is 99.91%, 86.19%, 72.36% and 99.91%, respectively. Correspondingly, the anti-coking ratio of TiO2 coating is 83.39%, 85.77%, 68.57 and 85.77%, respectively. Hence, the TiN coating has the better anti-coking performance than that of TiO2 coating. The morphologies of the cokes on 310S surface are mainly filamentous cokes, and TiN and TiO2 coatings inhibites the filamentous cokes formation.
In order to avoid the catalytic cokes forming, the TiN and TiO2 coating is directly deposited on the surface of the 310S stainless steel flake with the diameter of 10?10?0.9 mm by using atmospheric pressure chemical vapor deposition method. The deposition temperature is 850 ℃ for TiN and TiO2, respectively, and the deposition time is 2.5 h. The morphologies and structures of the coatings were analyzed by SEM, EDS and XRD, the results show that the TiN and TiO2 coating is continuous, close-packed and homogeneous; the titanium nitride in the coating had cub phase, Ti and N atomic ratio in the titanium nitride coating is 1:1, and the titanium oxide in the coating is the Ti2O3~Ti3O5 stoichiometrically. An atmospheric pressure cracking system was set up for evaluating the anti-coking property of TiN and TiO2 coating with n-hexane, cyclohexane, benzene and RP-3 as feedstock. The results show that TiN and TiO2 coating exhibit an excellent anti-coking performance, the anti-coking ratio of TiN coating for n-hexane, cyclohexane, benzene and RP-3 is 99.91%, 86.19%, 72.36% and 99.91%, respectively. Correspondingly, the anti-coking ratio of TiO2 coating is 83.39%, 85.77%, 68.57 and 85.77%, respectively. Hence, the TiN coating has the better anti-coking performance than that of TiO2 coating. The morphologies of the cokes on 310S surface are mainly filamentous cokes, and TiN and TiO2 coatings inhibites the filamentous cokes formation.
18 Effects of tensile deformation on microstructure and mechanical properties of Hastelloy C-276 alloy
2016, 45(12):3128-3134.
Abstract:
Abstract: The microstructural evolution and mechanical properties of Hastelloy C-276 alloy sheet with different deformations were investigated using the optical microscope (OM), electron back-scattered diffraction (EBSD), and tensile test. The results show that dislocation pile-ups and local strain concentration preferentially appear at grain boundaries under the deformation less than 14%. When deformation is in the range of 14~30%, a great quantity of dislocation was produced which located at twin boundaries and within grains, and the dislocation slip led to high strain concentration within grains. When deformation degree increasing from 0 to 30%, the strain concentration degree of grain boundaries increases at first then decreases, and reaches the maximum at 14%. The Ludwigson model can describe the true stress-true strain curves by the regression fitting. With the deformation degree increasing, the degree of work-hardening improved while the work-hardening rate decreased, and the critical strain of single slip transforming to multiple slip decreased.
Abstract: The microstructural evolution and mechanical properties of Hastelloy C-276 alloy sheet with different deformations were investigated using the optical microscope (OM), electron back-scattered diffraction (EBSD), and tensile test. The results show that dislocation pile-ups and local strain concentration preferentially appear at grain boundaries under the deformation less than 14%. When deformation is in the range of 14~30%, a great quantity of dislocation was produced which located at twin boundaries and within grains, and the dislocation slip led to high strain concentration within grains. When deformation degree increasing from 0 to 30%, the strain concentration degree of grain boundaries increases at first then decreases, and reaches the maximum at 14%. The Ludwigson model can describe the true stress-true strain curves by the regression fitting. With the deformation degree increasing, the degree of work-hardening improved while the work-hardening rate decreased, and the critical strain of single slip transforming to multiple slip decreased.
2016, 45(12):3135-3139.
Abstract:
We have preliminarily developed the part of experimental study about UF4 materials and its thermal chemical reaction characteristics in air, respectively with deferent analysis techniques such as micro-laser Raman spectroscopy(MLRS), X-ray photoelectron spectroscopy(XPS), weighing up and observing metallographs etc. Based on the physical and chemical properties of UF4 , we have obtained the Raman and XPS spectra of different uranium compounds after heating in stated temperature and time . The experimental results indicated that , UF4 sample is equivalent stable until it has been heated to 200 ℃ in air , and its Raman spectra was almost no change . But heated above 250 ℃ in air , the surface color of UF4 sample has obviously been changed , and there have been formed into multiform uranium compounds such as UO2、UO2F2、U3O8 etc with Raman and XPS analysis . On the other hand, the chemical reaction rate of UF4 in air was showed the trend from fast to slow.
We have preliminarily developed the part of experimental study about UF4 materials and its thermal chemical reaction characteristics in air, respectively with deferent analysis techniques such as micro-laser Raman spectroscopy(MLRS), X-ray photoelectron spectroscopy(XPS), weighing up and observing metallographs etc. Based on the physical and chemical properties of UF4 , we have obtained the Raman and XPS spectra of different uranium compounds after heating in stated temperature and time . The experimental results indicated that , UF4 sample is equivalent stable until it has been heated to 200 ℃ in air , and its Raman spectra was almost no change . But heated above 250 ℃ in air , the surface color of UF4 sample has obviously been changed , and there have been formed into multiform uranium compounds such as UO2、UO2F2、U3O8 etc with Raman and XPS analysis . On the other hand, the chemical reaction rate of UF4 in air was showed the trend from fast to slow.
2016, 45(12):3140-3143.
Abstract:
Ti/Al2O3 composites were synthesized by vacuum hot-pressing sintering, using the following sintering process as sintering temperature is 1420℃, time of heat preservation is 60 minutes, heating rate is 10℃ / min (0-1200℃) and 5℃ / min (1200℃-1420℃). The effects of carbon fiber on the mechanical property of Ti/Al2O3 composites are discussed. The results indicate that the carbon fiber can obviously effect the mechanical property of Ti/Al2O3 composites. When the carbon fiber content is 1.0 vol %, the relative density, micro-hardnessare,flexural strength and fracture toughness of the composite reach the maximum values of 97.62%, （16.6?.32）GPa , （381?1.25）GPa and （7.2?.19）MPa.m 1/2, respectively, and the fracture mode of the composites were optimised.
Ti/Al2O3 composites were synthesized by vacuum hot-pressing sintering, using the following sintering process as sintering temperature is 1420℃, time of heat preservation is 60 minutes, heating rate is 10℃ / min (0-1200℃) and 5℃ / min (1200℃-1420℃). The effects of carbon fiber on the mechanical property of Ti/Al2O3 composites are discussed. The results indicate that the carbon fiber can obviously effect the mechanical property of Ti/Al2O3 composites. When the carbon fiber content is 1.0 vol %, the relative density, micro-hardnessare,flexural strength and fracture toughness of the composite reach the maximum values of 97.62%, （16.6?.32）GPa , （381?1.25）GPa and （7.2?.19）MPa.m 1/2, respectively, and the fracture mode of the composites were optimised.
2016, 45(12):3144-3148.
Abstract:
Al-diffusion/YSZ thermal barrier coatings (TBCs) were deposited on Ti-Al alloys by electronic beam-physical vapor deposition (EB-PVD). The microstructure and phase constituent of the TBCs before and after high temperature oxidation were analyzed by SEM, EDS and XRD. And the high temperature oxidation resistance of the TBCs was measured. The results showed that the top YSZ TBCs were composed of non-equilibrium tetragonal t＇-ZrO2, which had a dense columnar microstructure. The high temperature oxidation resistance of TBCs was much higher than that of the substrate. The oxidation kinetics obeyed logarithmic law. The oxidation rates were 2.2?0-5mg/cm2.h and 1.14?0-3mg/cm2.h at 900℃ and 1000℃, respectively. During the high temperature oxidation, the element diffusion was occurred between the bond layers and the substrates and the interfaces were vanished. Thermal grown oxide (TGO) layers were formed between the surface layers and the bond layers.
Al-diffusion/YSZ thermal barrier coatings (TBCs) were deposited on Ti-Al alloys by electronic beam-physical vapor deposition (EB-PVD). The microstructure and phase constituent of the TBCs before and after high temperature oxidation were analyzed by SEM, EDS and XRD. And the high temperature oxidation resistance of the TBCs was measured. The results showed that the top YSZ TBCs were composed of non-equilibrium tetragonal t＇-ZrO2, which had a dense columnar microstructure. The high temperature oxidation resistance of TBCs was much higher than that of the substrate. The oxidation kinetics obeyed logarithmic law. The oxidation rates were 2.2?0-5mg/cm2.h and 1.14?0-3mg/cm2.h at 900℃ and 1000℃, respectively. During the high temperature oxidation, the element diffusion was occurred between the bond layers and the substrates and the interfaces were vanished. Thermal grown oxide (TGO) layers were formed between the surface layers and the bond layers.
2016, 45(12):3149-3154.
Abstract:
Abstract: A a series of WC-9Ni-xCr samples were prepared through traditional powder metallurgy method. The effects of Cr additive amount on the microstructure and properties of WC-9Ni cemented carbides were investigated using X-ray diffraction, scanning electron microscope, mechanical property tester and immersion corrosion tests. The results show that the addition of Cr tends to inhibite the grain growth of the WC grains, decrease the density and bending strength of WC-9Ni cemented carbides, and increase the hardness and immersion corrosion resistant properties in neutral water of the alloys. With the Cr content increases, the variation tendency of grain size, density, hardness, bending strength and corrosion resistant of the alloy slow down. Furthermore, extensive addition of Cr in WC–9Ni cemented carbides could resulted in the formation of a new phase—(Wx,Cr(1-x))2C, which is easy to become fracture source of the alloy. Combine the results of microstructure and properties: sample 3# with Cr addition of 1.2 wt. % exhibits a relatively comprehensive performance in the five group of samples.
Abstract: A a series of WC-9Ni-xCr samples were prepared through traditional powder metallurgy method. The effects of Cr additive amount on the microstructure and properties of WC-9Ni cemented carbides were investigated using X-ray diffraction, scanning electron microscope, mechanical property tester and immersion corrosion tests. The results show that the addition of Cr tends to inhibite the grain growth of the WC grains, decrease the density and bending strength of WC-9Ni cemented carbides, and increase the hardness and immersion corrosion resistant properties in neutral water of the alloys. With the Cr content increases, the variation tendency of grain size, density, hardness, bending strength and corrosion resistant of the alloy slow down. Furthermore, extensive addition of Cr in WC–9Ni cemented carbides could resulted in the formation of a new phase—(Wx,Cr(1-x))2C, which is easy to become fracture source of the alloy. Combine the results of microstructure and properties: sample 3# with Cr addition of 1.2 wt. % exhibits a relatively comprehensive performance in the five group of samples.
2016, 45(12):3155-3159.
Abstract:
The WC-12wt%Co plate-like grain cemented carbides were prepared from plate-like W Co C (carbon black) base mixed powders. Effects of addition of nanometer tungsten powders and sintering processes on the microstructures and properties of plate-like grain cemented carbides were researched. It showed that the relative density of the WC-12wt%Co plate-like WC grain cemented carbides were near complete densification reached to 97%, the hardness of the alloys were exhibited obvious anisotropy, increasing the sintering temperature and prolonging sintering time or addition of nanometer tungsten powders were favor to sintering densification and the formation of more plate-like WC grains.
The WC-12wt%Co plate-like grain cemented carbides were prepared from plate-like W Co C (carbon black) base mixed powders. Effects of addition of nanometer tungsten powders and sintering processes on the microstructures and properties of plate-like grain cemented carbides were researched. It showed that the relative density of the WC-12wt%Co plate-like WC grain cemented carbides were near complete densification reached to 97%, the hardness of the alloys were exhibited obvious anisotropy, increasing the sintering temperature and prolonging sintering time or addition of nanometer tungsten powders were favor to sintering densification and the formation of more plate-like WC grains.
2016, 45(12):3160-3166.
Abstract:
This paper reports a facile route for synthesizing PVP stabilized Pd/Ni bimetallic nanosol by chemical co-reduction process. The morphology, size, structure and composition of the resultant Pd/Ni bimetallic nanosol were characterized by transmission electron microscopy (TEM). The effects of amount of PVP, reducing agent and metal composition on the hydrolysis of NaBH4 were studied. The results indicate that the catalytic activities of the prepared Pd/Ni bimetallic nanocatalysts with an average size of 2 nm were superior to that of monometallic Pd nanocatalyst with the same size. The Pd10Ni90 bimetallic nanosol showed the highest catalytic activity with hydrogen generation rates of 8,250 mol-H?molPd-1?h-1 at 303 K, And the activation energy, enthalpy and entropy of Pd20Ni80 bimetallic nanoparticles 35.7 kJ/mol, 33.3 kJ/mol and -150 J/mol respectively. In addition, the prepared Pd/Ni bimetallic nanosol had a good catalytic activity even after the fourth cycle. The high catalytic activity of the Pd/Ni BNPs can be ascribed to electronic charge transfer effects. And DFT calculations showed that Pd atoms were indeed negatively charged with the positively charged Ni atoms. The positively charged Ni atoms and negatively charged Pd atoms acted as catalytic active sites for the hydrolysis of the alkaline NaBH4 solution.
This paper reports a facile route for synthesizing PVP stabilized Pd/Ni bimetallic nanosol by chemical co-reduction process. The morphology, size, structure and composition of the resultant Pd/Ni bimetallic nanosol were characterized by transmission electron microscopy (TEM). The effects of amount of PVP, reducing agent and metal composition on the hydrolysis of NaBH4 were studied. The results indicate that the catalytic activities of the prepared Pd/Ni bimetallic nanocatalysts with an average size of 2 nm were superior to that of monometallic Pd nanocatalyst with the same size. The Pd10Ni90 bimetallic nanosol showed the highest catalytic activity with hydrogen generation rates of 8,250 mol-H?molPd-1?h-1 at 303 K, And the activation energy, enthalpy and entropy of Pd20Ni80 bimetallic nanoparticles 35.7 kJ/mol, 33.3 kJ/mol and -150 J/mol respectively. In addition, the prepared Pd/Ni bimetallic nanosol had a good catalytic activity even after the fourth cycle. The high catalytic activity of the Pd/Ni BNPs can be ascribed to electronic charge transfer effects. And DFT calculations showed that Pd atoms were indeed negatively charged with the positively charged Ni atoms. The positively charged Ni atoms and negatively charged Pd atoms acted as catalytic active sites for the hydrolysis of the alkaline NaBH4 solution.
2016, 45(12):3167-3171.
Abstract:
A low cost nickel-based superalloy DD6 has been independently developed in our country which has excellent tensile properties, high-temperature creep resistance, fatigue resistance, oxidation and corrosion resistance. DD6 superalloy has broad application prospects in fields of turbine components. In order to establish failure evaluation standard of single crystal turbine blades, heat treatments are given to DD6 in this study to simulate the actual operating temperature of turbine blades. The microstructure evolution with temperature of DD6 superalloy after heated for 50 hours is studied and analyzed. It is found that γ′ phase continuously dissolved into γ base with the increase of heating temperature. It is related to the diffusion of Al, Ti elements from γ′ phase to γ base. While DD6 are cooling from above 1150 ℃ to room temperature, the second γ′ phase particles will precipitate at wide base tunnels and grow bigger with temperature rises. The precipitation of second γ′ phase is due to composition undercooling caused by oversaturation of Al, Ti in γ base. From the point of view of thermodynamics, second γ′ phase grow to decrease interface energy. And it is related with heating temperature and cooling time from the point of view of kinetics.
A low cost nickel-based superalloy DD6 has been independently developed in our country which has excellent tensile properties, high-temperature creep resistance, fatigue resistance, oxidation and corrosion resistance. DD6 superalloy has broad application prospects in fields of turbine components. In order to establish failure evaluation standard of single crystal turbine blades, heat treatments are given to DD6 in this study to simulate the actual operating temperature of turbine blades. The microstructure evolution with temperature of DD6 superalloy after heated for 50 hours is studied and analyzed. It is found that γ′ phase continuously dissolved into γ base with the increase of heating temperature. It is related to the diffusion of Al, Ti elements from γ′ phase to γ base. While DD6 are cooling from above 1150 ℃ to room temperature, the second γ′ phase particles will precipitate at wide base tunnels and grow bigger with temperature rises. The precipitation of second γ′ phase is due to composition undercooling caused by oversaturation of Al, Ti in γ base. From the point of view of thermodynamics, second γ′ phase grow to decrease interface energy. And it is related with heating temperature and cooling time from the point of view of kinetics.
zhangchangjiang
,
zhangshuzhi
,
houzhaoping
,
linpeng
,
kongfantao
,
chenyuyong
,
wudongxing
,
wangbin
2016, 45(12):3172-3176.
Abstract:
The effects of heat treatment on microstructure and mechanical properties of as forged 2.5vol.%(TiB TiC)/Ti composite have been studied in this paper. The results showed that solution and aging treatments have a significant impact on the matrix characteristics and tensile properties of the composite. Equiaxed, bimodal and fully lamellar microstructures were obtained, the content of primary α reduces while the content of the transformed β phase increases with increasing of solution temperature. The TiB and TiC reinforcements are stable during heat treatment and their morphologies and distribution have no obvious change. The tensile strength increases while the elongation decreases after solution and aging treatment. With increasing of solution temperatures, both the tensile strength and elongation rises at room temperature, while the tensile strength and elongation tested at 650 oC exhibit a contrary tendency. The composite presents superior comprehensive properties with tensile strength of 1215.8MPa and elongation of 3.14% at room temperature, while tensile strength of 629.9MPa and elongation of 15.9% at 650 oC after the heat treatment of 1100 oC/2h/AC 600 oC/6h/AC.
The effects of heat treatment on microstructure and mechanical properties of as forged 2.5vol.%(TiB TiC)/Ti composite have been studied in this paper. The results showed that solution and aging treatments have a significant impact on the matrix characteristics and tensile properties of the composite. Equiaxed, bimodal and fully lamellar microstructures were obtained, the content of primary α reduces while the content of the transformed β phase increases with increasing of solution temperature. The TiB and TiC reinforcements are stable during heat treatment and their morphologies and distribution have no obvious change. The tensile strength increases while the elongation decreases after solution and aging treatment. With increasing of solution temperatures, both the tensile strength and elongation rises at room temperature, while the tensile strength and elongation tested at 650 oC exhibit a contrary tendency. The composite presents superior comprehensive properties with tensile strength of 1215.8MPa and elongation of 3.14% at room temperature, while tensile strength of 629.9MPa and elongation of 15.9% at 650 oC after the heat treatment of 1100 oC/2h/AC 600 oC/6h/AC.
Fan Xue Yi
,
Wang Liang
,
Luo Liang Shun
,
Xu Ji Gang
,
Yi Hong Yong
,
Chen Ruirun
,
Zhou Guo Zhu
,
Wang Ning
,
Zhang Jian Bing
,
SuYan Qing
2016, 45(12):3177-3180.
Abstract:
The effect of local loading traveling magnetic field on shrinkage cavity and porosity and mechanical properties of ZL205A sheet casts was studied. The microstructure and mechanical properties were analyzed by scanning electron microscope and electronic universal material testing machine, respectively. Results show that under travelling magnetic field, the shrinkage cavity and porosity decrease greatly, and the tensile strength, yield strength and elongation increase from 436.61MPa, 390.22MPa and 3.29% to 470.24MPa, 416.97MPa and4.15%, respectively. The tensile strength and yield strength increase by 33.63MPa and 26.75MPa, and the elongation increases by 26.14%.
The effect of local loading traveling magnetic field on shrinkage cavity and porosity and mechanical properties of ZL205A sheet casts was studied. The microstructure and mechanical properties were analyzed by scanning electron microscope and electronic universal material testing machine, respectively. Results show that under travelling magnetic field, the shrinkage cavity and porosity decrease greatly, and the tensile strength, yield strength and elongation increase from 436.61MPa, 390.22MPa and 3.29% to 470.24MPa, 416.97MPa and4.15%, respectively. The tensile strength and yield strength increase by 33.63MPa and 26.75MPa, and the elongation increases by 26.14%.
2016, 45(12):3181-3185.
Abstract:
In this paper, Ni coated Yb2O3 composite powder was obtained by electroless plating. The W-Ni/Yb2O3 composite powder dispersed with different contents of Ni coated Yb2O3 composite powder was first fabricated by the mechanical alloying (MA) process, the powder was then pressed and sintered at 1600 ?C for 3 hours. Surface morphology of Ni coated Yb2O3 composite powder and the W-Ni/Yb2O3 composite material were observed by FE-SEM. Relative density, microhardness and thermal conductivity of W-Ni/Yb2O3 composite material were tested. The results show that the relative density and microhardness of W-Ni/Yb2O3 composite material enhance with the increase of Ni-Yb2O3 contents, and the addition of Ni coated Yb2O3 composite powder promotes the sintering densification of W-Ni/Yb2O3 composite material. At the same time, the addition of Ni coated Yb2O3 composite powder makes the grain size of tungsten based material refined, but reduces its thermal conductivity.
In this paper, Ni coated Yb2O3 composite powder was obtained by electroless plating. The W-Ni/Yb2O3 composite powder dispersed with different contents of Ni coated Yb2O3 composite powder was first fabricated by the mechanical alloying (MA) process, the powder was then pressed and sintered at 1600 ?C for 3 hours. Surface morphology of Ni coated Yb2O3 composite powder and the W-Ni/Yb2O3 composite material were observed by FE-SEM. Relative density, microhardness and thermal conductivity of W-Ni/Yb2O3 composite material were tested. The results show that the relative density and microhardness of W-Ni/Yb2O3 composite material enhance with the increase of Ni-Yb2O3 contents, and the addition of Ni coated Yb2O3 composite powder promotes the sintering densification of W-Ni/Yb2O3 composite material. At the same time, the addition of Ni coated Yb2O3 composite powder makes the grain size of tungsten based material refined, but reduces its thermal conductivity.
2016, 45(12):3186-3191.
Abstract:
In this paper, the hot-rolled AZ31 Mg alloy sheet was chosen as studied project, the effect of texture on slip and twin activations of Mg alloy samples during compression at room temperature was studied by electron backscatter diffraction technique (EBSD). The samples, machined from the rolled Mg alloy sheet, were compressed with the compression axes tilted 0°，30°，60° and 90° from the sheet normal direction, respectively. A high yield stress, without distinct yield platform, is observed for the 0° samples. The critical resolved shear stress (CRSS) of extension twin is higher than that of basal slip. The number of {10-12} extension twin was increased gradually with the increase of the angle. The plastic deformation of the 0° samples are mainly performed by slips due to inactive tension twin, and low-angle boundaries increase obviously. There are more low-angle boundaries in the 60° samples than 30° samples because of the activation of prismatic slip.
In this paper, the hot-rolled AZ31 Mg alloy sheet was chosen as studied project, the effect of texture on slip and twin activations of Mg alloy samples during compression at room temperature was studied by electron backscatter diffraction technique (EBSD). The samples, machined from the rolled Mg alloy sheet, were compressed with the compression axes tilted 0°，30°，60° and 90° from the sheet normal direction, respectively. A high yield stress, without distinct yield platform, is observed for the 0° samples. The critical resolved shear stress (CRSS) of extension twin is higher than that of basal slip. The number of {10-12} extension twin was increased gradually with the increase of the angle. The plastic deformation of the 0° samples are mainly performed by slips due to inactive tension twin, and low-angle boundaries increase obviously. There are more low-angle boundaries in the 60° samples than 30° samples because of the activation of prismatic slip.
2016, 45(12):3192-3196.
Abstract:
Q345-TA2 titanium-steel clad plate, because of its high strength and excellent corrosion resistance , has been more and more used in dynamic environment. In this paper, Applying the GLeeble - 3500 thermal simulation testing machine and split hopkinson pressure bar (SHPB) device, the quasi-static and high –strain- rate compression were carried out. The experimental results show that the Q345 - TA2 titanium-steel composite material has enhanced effect of strain rate, plasticizing effect and softening action of adiabatic temperature rise, but not very sensitive to strain rate change within the scope of the each partition of quasistatic and dynamic. Based on the considering of the adiabatic temperature rise, modifying the jaynes-cummings constitutive model, the fitting obtained can be used to analyze structure under the action of impact load of the material constitutive model, the results are good.
Q345-TA2 titanium-steel clad plate, because of its high strength and excellent corrosion resistance , has been more and more used in dynamic environment. In this paper, Applying the GLeeble - 3500 thermal simulation testing machine and split hopkinson pressure bar (SHPB) device, the quasi-static and high –strain- rate compression were carried out. The experimental results show that the Q345 - TA2 titanium-steel composite material has enhanced effect of strain rate, plasticizing effect and softening action of adiabatic temperature rise, but not very sensitive to strain rate change within the scope of the each partition of quasistatic and dynamic. Based on the considering of the adiabatic temperature rise, modifying the jaynes-cummings constitutive model, the fitting obtained can be used to analyze structure under the action of impact load of the material constitutive model, the results are good.
2016, 45(12):3197-3200.
Abstract:
The parameters of neutron diffraction stress measurement of beryllium on a steady-state reactor have been studied and optimized using a welded beryllium ring. The results show that under the condition of the neutron beam wavelength of 1.587? and neutron flux rate of 2?106ncm-2s-1, the neutron stress measurement for beryllium can use Be (110) plane, which the diffraction angle is 88.2o. The gauge volume is 2?2?2mm3. In the first test, the measuring time is 120s. After 4 runs test at a fixed location, it is found the diffraction curve has an obvious intensity fluctuation and the maximum strain error is about 300??. Afterwards, the measuring time extends to 6000s, the diffraction curve is smooth and has good repetitive. The maximum starin error decreases less than 50??, which the stress error for beryllium 15 MPa. The hoop strain in beryllium ring near the weld line has been measured using the optimized parameters, which indicates the hoop strain trend is basically identical to the literature. This study can establish a basis for the stress measurement of beryllium by neutron diffraction.
The parameters of neutron diffraction stress measurement of beryllium on a steady-state reactor have been studied and optimized using a welded beryllium ring. The results show that under the condition of the neutron beam wavelength of 1.587? and neutron flux rate of 2?106ncm-2s-1, the neutron stress measurement for beryllium can use Be (110) plane, which the diffraction angle is 88.2o. The gauge volume is 2?2?2mm3. In the first test, the measuring time is 120s. After 4 runs test at a fixed location, it is found the diffraction curve has an obvious intensity fluctuation and the maximum strain error is about 300??. Afterwards, the measuring time extends to 6000s, the diffraction curve is smooth and has good repetitive. The maximum starin error decreases less than 50??, which the stress error for beryllium 15 MPa. The hoop strain in beryllium ring near the weld line has been measured using the optimized parameters, which indicates the hoop strain trend is basically identical to the literature. This study can establish a basis for the stress measurement of beryllium by neutron diffraction.
2016, 45(12):3201-3206.
Abstract:
The flower-like precursor (CH3O)2Co microspheres assembled by nano-flakes were firstly fabricated by a solvothermal method using Co(Ac)2 as source materials in methanol system. Co3O4 porous microspheres with well-preserved morphologies were then achieved by calcining the precursor. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Thermal gravimetry (TG), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and N2 adsorption-desorption were used to characterize the phase, chemical composition, morphology and pore structure of the samples. Differential scanning calorimetry (DSC) was employed to evaluate the catalytic performance of these Co3O4 microspheres for thermal decomposition of ammonium perchlorate (AP). The result shows that the as-obtained Co3O4 microspheres exhibit excellent catalytic performance. Adding 2% (wt) Co3O4 microspheres into AP decreases the high-temperature exothermic peak by 122 癈 and the apparent decomposition heat increases by 422 J/g, respectively. The excellent catalytic activity is attributed to good dispersities and plentiful hierarchical pore structure of Co3O4 microspheres.
The flower-like precursor (CH3O)2Co microspheres assembled by nano-flakes were firstly fabricated by a solvothermal method using Co(Ac)2 as source materials in methanol system. Co3O4 porous microspheres with well-preserved morphologies were then achieved by calcining the precursor. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Thermal gravimetry (TG), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and N2 adsorption-desorption were used to characterize the phase, chemical composition, morphology and pore structure of the samples. Differential scanning calorimetry (DSC) was employed to evaluate the catalytic performance of these Co3O4 microspheres for thermal decomposition of ammonium perchlorate (AP). The result shows that the as-obtained Co3O4 microspheres exhibit excellent catalytic performance. Adding 2% (wt) Co3O4 microspheres into AP decreases the high-temperature exothermic peak by 122 癈 and the apparent decomposition heat increases by 422 J/g, respectively. The excellent catalytic activity is attributed to good dispersities and plentiful hierarchical pore structure of Co3O4 microspheres.
2016, 45(12):3207-3212.
Abstract:
Several different hydrogen storage systems including MgH2, MgH2-Graphene, MgH2-Ni and MgH2-Graphene-Ni were synthesized by high energy ball milling technique. The phase compositions, microstructures and dehydrogenation properties of the different systems were characterized by the testing methods such as X-ray diffraction, scanning electron microscope and differential scanning calorimeter. The effect and mechanism of dehydrogenation properties of MgH2 separate/multi-doped by Graphene and Ni were also studied systematically. It turned out that the initial dehydrogenation temperature of MgH2 doped by Graphene decreased by about 33℃ as a result of the effect of grain refinement and uniform size of MgH2 particles suffered from the structure confinement effect by Graphene in the ball-milling process. For the MgH2-Ni system, the initial dehydrogenation temperature of MgH2 significantly decreased by almost 136℃ due to the lattice deformation and the reduction of structural stability of MgH2 matrix where some Mg atoms were replaced by Ni atoms. However, the doping order played an important role in the Graphene and Ni multi-doped MgH2 system. When Graphene and Ni doped in the MgH2 system at the same time, the initial dehydrogenation temperature of MgH2 system did not reduce because the buffer function of MgH2 particle coated by Graphene made it difficult for the Ni atoms solid-soluted into the MgH2 matrix. While when Graphene doped in the MgH2 system after Ni atom, the initial dehydrogenation temperature further decreased by closely 175℃ with respect to pure MgH2 system due to both the effect of the realization of solid solution by Ni atom and the structure confinement effect by Graphene.
Several different hydrogen storage systems including MgH2, MgH2-Graphene, MgH2-Ni and MgH2-Graphene-Ni were synthesized by high energy ball milling technique. The phase compositions, microstructures and dehydrogenation properties of the different systems were characterized by the testing methods such as X-ray diffraction, scanning electron microscope and differential scanning calorimeter. The effect and mechanism of dehydrogenation properties of MgH2 separate/multi-doped by Graphene and Ni were also studied systematically. It turned out that the initial dehydrogenation temperature of MgH2 doped by Graphene decreased by about 33℃ as a result of the effect of grain refinement and uniform size of MgH2 particles suffered from the structure confinement effect by Graphene in the ball-milling process. For the MgH2-Ni system, the initial dehydrogenation temperature of MgH2 significantly decreased by almost 136℃ due to the lattice deformation and the reduction of structural stability of MgH2 matrix where some Mg atoms were replaced by Ni atoms. However, the doping order played an important role in the Graphene and Ni multi-doped MgH2 system. When Graphene and Ni doped in the MgH2 system at the same time, the initial dehydrogenation temperature of MgH2 system did not reduce because the buffer function of MgH2 particle coated by Graphene made it difficult for the Ni atoms solid-soluted into the MgH2 matrix. While when Graphene doped in the MgH2 system after Ni atom, the initial dehydrogenation temperature further decreased by closely 175℃ with respect to pure MgH2 system due to both the effect of the realization of solid solution by Ni atom and the structure confinement effect by Graphene.
2016, 45(12):3213-3217.
Abstract:
The relationship between oxide thickness and grain orientations was investigated using Zircaloy-4 coarse-grained specimens corroded at 500 ℃/10.3 MPa in superheated steam. The results indicate that the growth of the oxide films formed on Zircaloy-4 specimens shows remarkably anisotropic characteristics. The growth rate of the oxide films formed on the grain surfaces with the orientation between prismatic plane of (10-10) and (11-20) was fastest, and the nodular corrosion spots were formed earlier after 3 h exposure. The grain surfaces with the orientation whose poles were located at the middle of inverse pole figure started to form the nodular corrosion spots for 30 h exposure gradually. The thinnest oxide layers were detected on the grain surfaces with the orientation nearby basal plane (0001), and the nodular corrosion spots did not appeared after 30 h exposure. The experimental results show that the nodoular corrosion resistance of Zircaloy-4 is closely related to the grain orientations when the distribution and the size of second phase particles, and the solid solution content of Fe and Cr alloying elements in α-Zr matrix are at the same level.
The relationship between oxide thickness and grain orientations was investigated using Zircaloy-4 coarse-grained specimens corroded at 500 ℃/10.3 MPa in superheated steam. The results indicate that the growth of the oxide films formed on Zircaloy-4 specimens shows remarkably anisotropic characteristics. The growth rate of the oxide films formed on the grain surfaces with the orientation between prismatic plane of (10-10) and (11-20) was fastest, and the nodular corrosion spots were formed earlier after 3 h exposure. The grain surfaces with the orientation whose poles were located at the middle of inverse pole figure started to form the nodular corrosion spots for 30 h exposure gradually. The thinnest oxide layers were detected on the grain surfaces with the orientation nearby basal plane (0001), and the nodular corrosion spots did not appeared after 30 h exposure. The experimental results show that the nodoular corrosion resistance of Zircaloy-4 is closely related to the grain orientations when the distribution and the size of second phase particles, and the solid solution content of Fe and Cr alloying elements in α-Zr matrix are at the same level.
2016, 45(12):3218-3222.
Abstract:
Nano-Ce / CuO desulfurizers modified by iron, cobalt and zinc were prepared by direct deposition precipitation, and the performance of the nanoparticles for H2S desulfurization at ambient temperature was evaluated by the break-through tests. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and other characterization means were adopted to explore relationship between structural changes and desulfurization performance. The results indicate that nano-Ce / CuO desulfurizer modified by cobalt has the best desulfurization activity, and decreased significantly in particle size, and increased in the molar ratio of Cu3 /Cu2 , which was in favor of the oxygen vacancies increased in the surface; When the addition amount of Co in Ce / Cu desulfurizer is 4.9%, it exhibits best desulfurization activity with a H2S breakthrough time of 525 min, this extended nearly more 300 min than Ce / CuO desulfurizer.
Nano-Ce / CuO desulfurizers modified by iron, cobalt and zinc were prepared by direct deposition precipitation, and the performance of the nanoparticles for H2S desulfurization at ambient temperature was evaluated by the break-through tests. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and other characterization means were adopted to explore relationship between structural changes and desulfurization performance. The results indicate that nano-Ce / CuO desulfurizer modified by cobalt has the best desulfurization activity, and decreased significantly in particle size, and increased in the molar ratio of Cu3 /Cu2 , which was in favor of the oxygen vacancies increased in the surface; When the addition amount of Co in Ce / Cu desulfurizer is 4.9%, it exhibits best desulfurization activity with a H2S breakthrough time of 525 min, this extended nearly more 300 min than Ce / CuO desulfurizer.
2016, 45(12):3223-3226.
Abstract:
The Sm3 doped Co2Z-type hexagonal ferrite materials were prepared by the conventional ceramic method and the microstructures and microwave absorbing properties of the materials were investigated. The influence of a certain amount of Sm3 addition on structures and microwave absorbing properties of the materials were investigated. The results show that Co2Z-type hexaferrite is still main phase in the Co2Z ferrite materials doped with Sm3 . It is observed that Sm-rich phase with granular morphology is dispersed in the main phase. The Sm3 doped Co2Z ferrite exhibited better microwave absorbing properties than the Sm3 undoped one. The maximum reflection loss of Sm3 doped Co2Z ferrite reached -20dB at 6.3GHz，and the frequency bandwidth of reflection loss more than 10 dB was 5GHz. The wave absorbing coating had good mechanical property and the adhesions of the coatings were higher than 10MPa.
The Sm3 doped Co2Z-type hexagonal ferrite materials were prepared by the conventional ceramic method and the microstructures and microwave absorbing properties of the materials were investigated. The influence of a certain amount of Sm3 addition on structures and microwave absorbing properties of the materials were investigated. The results show that Co2Z-type hexaferrite is still main phase in the Co2Z ferrite materials doped with Sm3 . It is observed that Sm-rich phase with granular morphology is dispersed in the main phase. The Sm3 doped Co2Z ferrite exhibited better microwave absorbing properties than the Sm3 undoped one. The maximum reflection loss of Sm3 doped Co2Z ferrite reached -20dB at 6.3GHz，and the frequency bandwidth of reflection loss more than 10 dB was 5GHz. The wave absorbing coating had good mechanical property and the adhesions of the coatings were higher than 10MPa.
37 Microstructure of as-cast billet and homogenization treatment of 2A70 heat-resistance aluminum alloy
2016, 45(12):3227-3232.
Abstract:
The microstructure of casting billet and the homogenization treatment were investigated by optical microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction analysis (XRD) respectively. Meanwhile, using the Thermo-Calc software, the solidification path for the Al-2.4Cu-1.5 Mg-1.1Fe-1.1Ni alloy was calculated. On this basis, the phases precipitated during solidification were analyzed and the transition temperature of the non-equilibrium eutectic phases was also calculated, which provided a theoretical basis for the research on microstructure and homogenization process. According to the calculated results, the α-Al、Al2CuMg、Al2Cu、Al9FeNi、Al7Cu4Ni and Al7Cu2Fe phases are exist in the 2A70 alloy, which in accordance with the experimental findings. In addition, the transition temperature for the non-equilibrium eutectic phases can be approximate substituted by the computed data. The reasonable homogenization treatment process for the investigated alloy is 490℃?2~16h 520℃?2h. During the high-temperature and long-time homogenization process, the non-equilibrium eutectic phases are dissolved completely and the Al9FeNi、Al7Cu4Ni and Al7Cu2Fe changes a little.
The microstructure of casting billet and the homogenization treatment were investigated by optical microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction analysis (XRD) respectively. Meanwhile, using the Thermo-Calc software, the solidification path for the Al-2.4Cu-1.5 Mg-1.1Fe-1.1Ni alloy was calculated. On this basis, the phases precipitated during solidification were analyzed and the transition temperature of the non-equilibrium eutectic phases was also calculated, which provided a theoretical basis for the research on microstructure and homogenization process. According to the calculated results, the α-Al、Al2CuMg、Al2Cu、Al9FeNi、Al7Cu4Ni and Al7Cu2Fe phases are exist in the 2A70 alloy, which in accordance with the experimental findings. In addition, the transition temperature for the non-equilibrium eutectic phases can be approximate substituted by the computed data. The reasonable homogenization treatment process for the investigated alloy is 490℃?2~16h 520℃?2h. During the high-temperature and long-time homogenization process, the non-equilibrium eutectic phases are dissolved completely and the Al9FeNi、Al7Cu4Ni and Al7Cu2Fe changes a little.
2016, 45(12):3233-3237.
Abstract:
Plasma surface alloying process was employed to prepare molybdenizing coating on TC4 alloy. Microstructural characteristics of the molybdenizing coating were analyzed using optical microscope (OM), glow discharge optical emission spectrometer analysis (GDOES) and X-ray diffraction (XRD). Corrosion resistance of molybdenizing coating and TC4 alloy in simulated oilfield medium were estimatted via electrochemical measurements. The results revealed that the uniform and continuous molybdenizing coating was composed of a deposition layer and a diffusion layer. The molybdenizing coating presented slightly lower corrosion resistance as compared with TC4 alloy.
Plasma surface alloying process was employed to prepare molybdenizing coating on TC4 alloy. Microstructural characteristics of the molybdenizing coating were analyzed using optical microscope (OM), glow discharge optical emission spectrometer analysis (GDOES) and X-ray diffraction (XRD). Corrosion resistance of molybdenizing coating and TC4 alloy in simulated oilfield medium were estimatted via electrochemical measurements. The results revealed that the uniform and continuous molybdenizing coating was composed of a deposition layer and a diffusion layer. The molybdenizing coating presented slightly lower corrosion resistance as compared with TC4 alloy.
2016, 45(12):3238-3244.
Abstract:
Evolution of chemical composition during phase decomposition and growth and the mechanisms of the directional interface migration during exterior load for Ni75Al7.5V17.5 alloy was investigated in this study, which is based on microscopic phase-field method. The results show that V which is needed for the growth of DO22 in the early stage came form the ordering domain among L12, V came from the interior of L12 in the later stage, and the speed for DO22 in the early stage was faster than it in the later stage. They formed five types of interfaces, and A-type was the main type for interface migration. It had a few A and B type interface in the early stage, and morphology changed little. With the rise of the number for A-type interface, the growth and decomposition for phases were accelerated, the number of A-type interface reduced and the number of B-type interface increased, and alloy reached balance fainlly. A-type interface migrated along stress during compress strees so that DO22 grew along this direction, and rafting structure of alloy formed.
Evolution of chemical composition during phase decomposition and growth and the mechanisms of the directional interface migration during exterior load for Ni75Al7.5V17.5 alloy was investigated in this study, which is based on microscopic phase-field method. The results show that V which is needed for the growth of DO22 in the early stage came form the ordering domain among L12, V came from the interior of L12 in the later stage, and the speed for DO22 in the early stage was faster than it in the later stage. They formed five types of interfaces, and A-type was the main type for interface migration. It had a few A and B type interface in the early stage, and morphology changed little. With the rise of the number for A-type interface, the growth and decomposition for phases were accelerated, the number of A-type interface reduced and the number of B-type interface increased, and alloy reached balance fainlly. A-type interface migrated along stress during compress strees so that DO22 grew along this direction, and rafting structure of alloy formed.
2016, 45(12):3245-3249.
Abstract:
There are three variants of precipitate in Al-Cu alloy, and these variants are parallel or perpendicular to the external stress direction. As many reserchers assumed that the external stress is parallel or perpendicular to the precipitate, however the external stress may have a certain angle with the precipitate for some aluminum alloys. Therefore, a new model is proposed in this paper with the consideration of the angle between precipitate and stress, which can give a method to judge the stress orientation effect of the precipitate. Transmission electronic microscopy (TEM) and Scanning transmission electronic microscopy (STEM) are employed in this paper to analyze the precipitate in the aged Al-4Cu alloy under applied stress. The results proved that the existence of the stress orientation effect of GP zones and θ″ phase. It is employed the new model to analyze the stress orientation effect and this model can provide a convinient method to prove whether there is stress orientation effect, which can also be applied to other series aluminum alloy.
There are three variants of precipitate in Al-Cu alloy, and these variants are parallel or perpendicular to the external stress direction. As many reserchers assumed that the external stress is parallel or perpendicular to the precipitate, however the external stress may have a certain angle with the precipitate for some aluminum alloys. Therefore, a new model is proposed in this paper with the consideration of the angle between precipitate and stress, which can give a method to judge the stress orientation effect of the precipitate. Transmission electronic microscopy (TEM) and Scanning transmission electronic microscopy (STEM) are employed in this paper to analyze the precipitate in the aged Al-4Cu alloy under applied stress. The results proved that the existence of the stress orientation effect of GP zones and θ″ phase. It is employed the new model to analyze the stress orientation effect and this model can provide a convinient method to prove whether there is stress orientation effect, which can also be applied to other series aluminum alloy.
2016, 45(12):3250-3254.
Abstract:
Continuous brazing with ultra-high frequency induction was proposed to braze the monocrystalline diamond grains using Ag-Cu-Ti filler alloy. The interfacial microstructure and residual stress of the brazed diamond was investigated and analogized by scanning electron microscopy (SEM) and Raman spectroscope. The experimental results revealed the fact that the formation of TiC crystal was in non-equilibrium state during continuous brazing with ultra-high frequency induction. The morphology of the formed TiC appared granular and island-like structure, far away from the equilibrium state. A little dendrite with Cu-riched was observed in filler alloy, and martensite was formed near the surface of steel substrate. The maximum compressive stress in the brazed diamond was 500MPa at the top, while the maximum tensile stress is 150MPa at the bottom. This result was opposite to the residual stress distribution obtained by furnace brazing.
Continuous brazing with ultra-high frequency induction was proposed to braze the monocrystalline diamond grains using Ag-Cu-Ti filler alloy. The interfacial microstructure and residual stress of the brazed diamond was investigated and analogized by scanning electron microscopy (SEM) and Raman spectroscope. The experimental results revealed the fact that the formation of TiC crystal was in non-equilibrium state during continuous brazing with ultra-high frequency induction. The morphology of the formed TiC appared granular and island-like structure, far away from the equilibrium state. A little dendrite with Cu-riched was observed in filler alloy, and martensite was formed near the surface of steel substrate. The maximum compressive stress in the brazed diamond was 500MPa at the top, while the maximum tensile stress is 150MPa at the bottom. This result was opposite to the residual stress distribution obtained by furnace brazing.
2016, 45(12):3255-3261.
Abstract:
The glassy ribbons and bulk cylinders with the same compositions were prepared by suction casting and melt spinning, respectively. The influences of cooling rate on the microstructure, thermal stability and mechanical properties of metallic glasses were studied by Differential Scanning Calorimetry, HRTEM and Nano Indenter. The type of the short ordered clusters in the glassy ribbons are the same as those in the glassy bulk cylinders, but more ordered clusters and less free volume can form in later because of the lower cooling rate during preparation. Consequently, the glassy ribbons have higher thermal stability, yield strength, Young''s Modulusr and hardness than the glassy bulk cylinders.
The glassy ribbons and bulk cylinders with the same compositions were prepared by suction casting and melt spinning, respectively. The influences of cooling rate on the microstructure, thermal stability and mechanical properties of metallic glasses were studied by Differential Scanning Calorimetry, HRTEM and Nano Indenter. The type of the short ordered clusters in the glassy ribbons are the same as those in the glassy bulk cylinders, but more ordered clusters and less free volume can form in later because of the lower cooling rate during preparation. Consequently, the glassy ribbons have higher thermal stability, yield strength, Young''s Modulusr and hardness than the glassy bulk cylinders.
2016, 45(12):3262-3266.
Abstract:
In the present work，normal carbon source black carbon was substituted by graphene which was dispersed in N-Methyl-2-pyrrolidone and was used to prepare nanocrystalline WC-Co composite powders using short process in-situ reduction and carbonization reaction method. The results show that graphene as carbon source could reduce reaction temperature, and the particles diameter of WC-Co composite powders distribute slightly. Composite powders were consolidated through spark plasma sintering system and the mean grain size of WC in WC-Co cemented carbides is about 290nm. Vickers hardness and fracture toughness of the bulk was 1387.7?3.1kg/mm2 and 8.3?.1MPa?m1/2. The interfaces between WC/WC, WC/Co and WC/C were studied through HRTEM images and had grain boundaries with low misfit.
In the present work，normal carbon source black carbon was substituted by graphene which was dispersed in N-Methyl-2-pyrrolidone and was used to prepare nanocrystalline WC-Co composite powders using short process in-situ reduction and carbonization reaction method. The results show that graphene as carbon source could reduce reaction temperature, and the particles diameter of WC-Co composite powders distribute slightly. Composite powders were consolidated through spark plasma sintering system and the mean grain size of WC in WC-Co cemented carbides is about 290nm. Vickers hardness and fracture toughness of the bulk was 1387.7?3.1kg/mm2 and 8.3?.1MPa?m1/2. The interfaces between WC/WC, WC/Co and WC/C were studied through HRTEM images and had grain boundaries with low misfit.
Liang Chaolong
,
Zhang Xin
,
liu hongliang
,
Zhang Fanxing
,
Wang Yang
,
Zheng Liang
,
Zhang Jiuxing
2016, 45(12):3267-3270.
Abstract:
In this paper, GdB6and CeB6 were used as raw materials,and hexaborides GdxCe1-xB6(x=0.0-1.0) bulk materials were successfully prepared by the spark plasma sintering (SPS). The effects of Gd doping on the phase composition, the mechanical properties, the resistivity and the thermionic emission properties of CeB6 base material were studied systematically. The research results show that high density GdxCe1-xB6 single-phase block material can be obtained by sintering at a temperature of 1550 oC, pressure of 50 MPa and holding time 5 min And the Vickers hardness of sintered samples can reach 24.02 Gpa.The thermionic emission properties results show that the right amount of Gd doped can significantly improve the electron emission properties of bulk materials, Gd0.1Ce0.9B6 composition block has the best thermal emission properties, of which the emission current density is 101.57A/cm2, the zero field current density is 21.94A/cm2 under an applied voltage condition of 4kV at 1600 oC, and is better than GdB6 and CeB6 block sample under the same conditions.
In this paper, GdB6and CeB6 were used as raw materials,and hexaborides GdxCe1-xB6(x=0.0-1.0) bulk materials were successfully prepared by the spark plasma sintering (SPS). The effects of Gd doping on the phase composition, the mechanical properties, the resistivity and the thermionic emission properties of CeB6 base material were studied systematically. The research results show that high density GdxCe1-xB6 single-phase block material can be obtained by sintering at a temperature of 1550 oC, pressure of 50 MPa and holding time 5 min And the Vickers hardness of sintered samples can reach 24.02 Gpa.The thermionic emission properties results show that the right amount of Gd doped can significantly improve the electron emission properties of bulk materials, Gd0.1Ce0.9B6 composition block has the best thermal emission properties, of which the emission current density is 101.57A/cm2, the zero field current density is 21.94A/cm2 under an applied voltage condition of 4kV at 1600 oC, and is better than GdB6 and CeB6 block sample under the same conditions.
2016, 45(12):3271-3277.
Abstract:
The influence of the aging treatment on microstructures and mechanical properties of 2099 Al-Li alloy were investigated by means of transmission electron microscopy, tensile properties measurement and slow strain rate test. There were one T6 temper and two T8 tempers in this study. The value of tensile strength in T8 tempers were both higher than that in T6 temper. With pre-deformation before the aging treatment, it increased the dislocation density, and therefore the number of T1 precipitate in matrix. Meanwhile, the duplex aging in T8 temper was equipped with better comprehensive property. In investigated of slow strain rate test of 2099 alloy, the loss of strength did not happen in this study. However, compared with samples tested in the air, the failure time rapidly decreased when samples tested in aqueous solution. The tensile strength, yield strength and elongation of alloy in T8 duplex aging condition were 590 MPa, 570 MPa, and 9.3%, respectively. 2099 alloy had excellent stress corrosion cracking resistance and no stress loss happened.
The influence of the aging treatment on microstructures and mechanical properties of 2099 Al-Li alloy were investigated by means of transmission electron microscopy, tensile properties measurement and slow strain rate test. There were one T6 temper and two T8 tempers in this study. The value of tensile strength in T8 tempers were both higher than that in T6 temper. With pre-deformation before the aging treatment, it increased the dislocation density, and therefore the number of T1 precipitate in matrix. Meanwhile, the duplex aging in T8 temper was equipped with better comprehensive property. In investigated of slow strain rate test of 2099 alloy, the loss of strength did not happen in this study. However, compared with samples tested in the air, the failure time rapidly decreased when samples tested in aqueous solution. The tensile strength, yield strength and elongation of alloy in T8 duplex aging condition were 590 MPa, 570 MPa, and 9.3%, respectively. 2099 alloy had excellent stress corrosion cracking resistance and no stress loss happened.
2016, 45(12):3278-3283.
Abstract:
3D network structured TiBw/Ti60 composite has been fabricated by reaction hot pressing. The high temperature mechanical properties of the composite were tested in the temperature range of 600~750 ℃. When compared to the Ti60 alloy, the high temperature strength of the composite can be significantly increased by the formation of in situ TiB whiskers with 3D network structure. The ultimate tensile strength of the 5.1 vol.%TiBw/Ti60 composite is increased by 42.5%, 39.9%, 35% and 13.2% compared with that of the Ti60 alloy at 600 ℃, 650 ℃, 700 ℃ and 750 ℃, respectively. However, the elongations of the composite are all lower than those of the matrix alloy. The main crack propagation of the composite with network structure follows the boundary along the network structure. And the fracture mechanism of the composite changes with increasing the experimental temperatures.
3D network structured TiBw/Ti60 composite has been fabricated by reaction hot pressing. The high temperature mechanical properties of the composite were tested in the temperature range of 600~750 ℃. When compared to the Ti60 alloy, the high temperature strength of the composite can be significantly increased by the formation of in situ TiB whiskers with 3D network structure. The ultimate tensile strength of the 5.1 vol.%TiBw/Ti60 composite is increased by 42.5%, 39.9%, 35% and 13.2% compared with that of the Ti60 alloy at 600 ℃, 650 ℃, 700 ℃ and 750 ℃, respectively. However, the elongations of the composite are all lower than those of the matrix alloy. The main crack propagation of the composite with network structure follows the boundary along the network structure. And the fracture mechanism of the composite changes with increasing the experimental temperatures.
2016, 45(12):3284-3289.
Abstract:
The aim of this study was to investigate the effects of laser peening (LP) on the micro-structural characteristics and high-temperature performance of IN718 nickel-based alloy. Firstly, LP process was performed on the standard tensile specimens at ambient temperature, then the treated specimens were exposed at 700 ℃ for 300 min. As comparison, we detected the surface residual stress and nano hardness on the untreated, LPed and heat-exposure specimens respectively. The corresponding micro-structures were also observed. The results indicate that high amplitude compressive residual stress distributed in the LP treated surface, the maximum value was -706 MPa, appearing in the central region of the LP area. LP process significantly increased nano hardness of treated surface, the average nano hardness was enhanced by 67.4%. Both the residual stress and nano hardness decreased after heat exposure, however, the strengthening effect still existed while compared with untreated specimens. An obvious “layer-seperating” phenomenon on the grain morphology in the depth direction was observed after laser peening. The grain size in the plastic deforming layer refined greatly, the affecting depth of which reached a value of 80 μm. The precipitated δ phase was found in the grain boundaries for the heat-exposure samples. A further observation verified that the interaction of mechanical twins and dislocation resulted in the grain refinement. After heat exposure, the single- directional-distributed dislocation array in the grain well verified the dislocation activities, which indicates that LP can inhibit the grain growing of IN718 alloy at high temperature.
The aim of this study was to investigate the effects of laser peening (LP) on the micro-structural characteristics and high-temperature performance of IN718 nickel-based alloy. Firstly, LP process was performed on the standard tensile specimens at ambient temperature, then the treated specimens were exposed at 700 ℃ for 300 min. As comparison, we detected the surface residual stress and nano hardness on the untreated, LPed and heat-exposure specimens respectively. The corresponding micro-structures were also observed. The results indicate that high amplitude compressive residual stress distributed in the LP treated surface, the maximum value was -706 MPa, appearing in the central region of the LP area. LP process significantly increased nano hardness of treated surface, the average nano hardness was enhanced by 67.4%. Both the residual stress and nano hardness decreased after heat exposure, however, the strengthening effect still existed while compared with untreated specimens. An obvious “layer-seperating” phenomenon on the grain morphology in the depth direction was observed after laser peening. The grain size in the plastic deforming layer refined greatly, the affecting depth of which reached a value of 80 μm. The precipitated δ phase was found in the grain boundaries for the heat-exposure samples. A further observation verified that the interaction of mechanical twins and dislocation resulted in the grain refinement. After heat exposure, the single- directional-distributed dislocation array in the grain well verified the dislocation activities, which indicates that LP can inhibit the grain growing of IN718 alloy at high temperature.
2016, 45(12):3290-3294.
Abstract:
The phase composition and resistivity of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe alloy undergone with different heat treatment process were studied, and the effects of heat treatment on thickness, roughness, micro morphology and phase composition of micro-arc oxidation coating were analyzed. The results show that the phase composition of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe alloy is changed by different heat treatment. The resistivity of alloy is slight decrease after heat treatment. With the solidSsolutionSheat treatment of 850 ℃, the minimum thickness and roughness of the micro-arc oxidation coating is 48.3 μm and 7.45μm which is obtained respectively. By the observation of morphology of oxidation coating, the crack is less and coating is compact with 750 ℃ and 850℃ solid solution heat treatment. XRD analysis shows that micro-arc oxidation coating is composed of anatase TiO2 and rutile TiO2.
The phase composition and resistivity of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe alloy undergone with different heat treatment process were studied, and the effects of heat treatment on thickness, roughness, micro morphology and phase composition of micro-arc oxidation coating were analyzed. The results show that the phase composition of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe alloy is changed by different heat treatment. The resistivity of alloy is slight decrease after heat treatment. With the solidSsolutionSheat treatment of 850 ℃, the minimum thickness and roughness of the micro-arc oxidation coating is 48.3 μm and 7.45μm which is obtained respectively. By the observation of morphology of oxidation coating, the crack is less and coating is compact with 750 ℃ and 850℃ solid solution heat treatment. XRD analysis shows that micro-arc oxidation coating is composed of anatase TiO2 and rutile TiO2.
2016, 45(12):3295-3301.
Abstract:
The TA15 titanium alloy plates were prepared by laser deposition manufacturing using TA15 titanium alloy powder. The effect of annealing treatment and deposition direction on microstructure, and mechanical properties of laser deposition manufacturing TA15 titanium alloy and alpha phase deformation mechanism has been studied. The experimental results showed that the length-width ratio of alpha phase in microstructure shows risen when increasing the annealing temperature; the mechanical properties are different in deposition direction and vertical deposition direction; the tensile strength in the deposition direction is obviously lower than that in the vertical direction; columnar crystal grain boundary has a baffling effect on alpha lamellar distortion; alpha lamellar deformation or fracture by extrusion and slippage; different directions have different tensile fracture modes, deposition direction is ductile fracture, vertical deposition direction is semi-cleavage and semi-ductile fracture.
The TA15 titanium alloy plates were prepared by laser deposition manufacturing using TA15 titanium alloy powder. The effect of annealing treatment and deposition direction on microstructure, and mechanical properties of laser deposition manufacturing TA15 titanium alloy and alpha phase deformation mechanism has been studied. The experimental results showed that the length-width ratio of alpha phase in microstructure shows risen when increasing the annealing temperature; the mechanical properties are different in deposition direction and vertical deposition direction; the tensile strength in the deposition direction is obviously lower than that in the vertical direction; columnar crystal grain boundary has a baffling effect on alpha lamellar distortion; alpha lamellar deformation or fracture by extrusion and slippage; different directions have different tensile fracture modes, deposition direction is ductile fracture, vertical deposition direction is semi-cleavage and semi-ductile fracture.
2016, 45(12):3302-3305.
Abstract:
Hydrogen anti-permeation coatings were formed by chemical reaction using urea and zirconium hydride at a high temperature range. The composition and depth of elements, bond state were analyzed by auger electron spectroscopy(AES) and X-ray photoelectron spectroscopy(XPS) technique. The results indicate that the thickness of coating, which is mainly composed of carbon, nitrogen, oxygen and zirconium, is 3.4μm, of which including nitrogen and carbon the thickness is about 150nm. It shows that the atomic concentration of carbon and nitrogen decreased continuously, while, oxygen and zirconium increased. XPS shows that coating was including ZrO2, and Zr-OH, Zr-N, C-H, N-H bonds. The mechanism of hydrogen resistance maybe that hydrogen was seized by carbon, nitrogen and oxygen to form C-H, O-H and N-H bonds while it diffuses from zirconium hydrides.
Hydrogen anti-permeation coatings were formed by chemical reaction using urea and zirconium hydride at a high temperature range. The composition and depth of elements, bond state were analyzed by auger electron spectroscopy(AES) and X-ray photoelectron spectroscopy(XPS) technique. The results indicate that the thickness of coating, which is mainly composed of carbon, nitrogen, oxygen and zirconium, is 3.4μm, of which including nitrogen and carbon the thickness is about 150nm. It shows that the atomic concentration of carbon and nitrogen decreased continuously, while, oxygen and zirconium increased. XPS shows that coating was including ZrO2, and Zr-OH, Zr-N, C-H, N-H bonds. The mechanism of hydrogen resistance maybe that hydrogen was seized by carbon, nitrogen and oxygen to form C-H, O-H and N-H bonds while it diffuses from zirconium hydrides.
2016, 45(12):3306-3312.
Abstract:
With double-layer structure thermal barrier coatings(TBCs) as the research object, three dimensional(3D) structure characteristics of TBCs such as morphology, composition, thickness, pores and porosity were researched by 3D X-ray microscopy and image processing technique. High resolution CT images of layered structure TBCs were reconstructed by 3D imaging method, 3D morphology of ceramic topcoat, bond coat and substrate were obtained by 3D segmentation and extraction, quantitative analysis of the important characterization parameters of TBCs such as thickness, pore size, pore number and porosity was performed. The results showed that the thickness of TBCs by 3D X-ray microscopy was basically consistent with the results of SEM, and the porosity was affected by the accuracy of the reconstruction.
With double-layer structure thermal barrier coatings(TBCs) as the research object, three dimensional(3D) structure characteristics of TBCs such as morphology, composition, thickness, pores and porosity were researched by 3D X-ray microscopy and image processing technique. High resolution CT images of layered structure TBCs were reconstructed by 3D imaging method, 3D morphology of ceramic topcoat, bond coat and substrate were obtained by 3D segmentation and extraction, quantitative analysis of the important characterization parameters of TBCs such as thickness, pore size, pore number and porosity was performed. The results showed that the thickness of TBCs by 3D X-ray microscopy was basically consistent with the results of SEM, and the porosity was affected by the accuracy of the reconstruction.
2016, 45(12):3313-3318.
Abstract:
The microstructure of two types of Zr-0.8Sn-1Nb-0.3Fe alloys prepared with different processes developed by Nuclear Power Institute of China was analyzed using optical microscope and transmission electron microscopy. The experiment results showed that with increasing of cold rolling and annealing times, the crystal grain of Zr alloy became much larger and much more non-uniformly in size. The average size of crystal grain grew from 3.9μm to 6.0μm. Further, the size of precipitates also became larger and the dispersion degree became much more non-uniformly, the average size of precipitates grew from 74.6nm to 89.6nm. Increaseing the cold rolling and annealing times could induce more Nb separating out from the matrix. The average of Nb/Fe ratio of precipitates increased from 1.17 to 1.39. Most of precipitates in Zr matrix were (Zr,Nb)2Fe compounds with FCC structure. Besides, a few of Zr(Nb,Fe)2 precipitates with HCP structure were also observed in the alloy increased of cold rolling and annealing times, but their size was much smaller. It was very important effect of the cold rolling and annealing processes on the microstructure of Zr alloys.
The microstructure of two types of Zr-0.8Sn-1Nb-0.3Fe alloys prepared with different processes developed by Nuclear Power Institute of China was analyzed using optical microscope and transmission electron microscopy. The experiment results showed that with increasing of cold rolling and annealing times, the crystal grain of Zr alloy became much larger and much more non-uniformly in size. The average size of crystal grain grew from 3.9μm to 6.0μm. Further, the size of precipitates also became larger and the dispersion degree became much more non-uniformly, the average size of precipitates grew from 74.6nm to 89.6nm. Increaseing the cold rolling and annealing times could induce more Nb separating out from the matrix. The average of Nb/Fe ratio of precipitates increased from 1.17 to 1.39. Most of precipitates in Zr matrix were (Zr,Nb)2Fe compounds with FCC structure. Besides, a few of Zr(Nb,Fe)2 precipitates with HCP structure were also observed in the alloy increased of cold rolling and annealing times, but their size was much smaller. It was very important effect of the cold rolling and annealing processes on the microstructure of Zr alloys.
2016, 45(12):3319-3324.
Abstract:
The fatigue crack propagation（FCP） behaviors of 2A97 aluminum-lithium alloy under different aging conditions were investigated. The microstructures and fracture morphologies were observed and analyzed by TEM 、SEM and OM. The results indicate that （T3 135℃/12h）aging treatment alloy has the minimum FCP rate，followed by T3；（T3 135℃/60h）aging treatment has a slightly slower fatigue crack propagation rate than （T3 135℃/120h）;T6 temper has the maximum FCP rate. Aging conditions have a significant influence on the FCP in low ΔK level，but not in high ΔK level. The δ?and fine T1 phases can enable slip planarity so as to enhance the reversibility of cyclic slip and reduce damage accumulation and stress intensity around the crack tip；slip planarity can also lead to the deflection of crack path and promote the crack closure effect.All these things result in an improvement of crack propagation resistance.Coarse and intensive T1 phase and semi-coherent θ?restrain slip planarity and easily induces stress intensity which can reduce crack propagation resistance.The Precipitation free zone(PFZ) and equilibrium phases at grain boundaries dramaticly reduce the strength of grain boundaries and lead to intergranular fracture ；this arouses greatly improvement in fatigue crack propagation rate.
The fatigue crack propagation（FCP） behaviors of 2A97 aluminum-lithium alloy under different aging conditions were investigated. The microstructures and fracture morphologies were observed and analyzed by TEM 、SEM and OM. The results indicate that （T3 135℃/12h）aging treatment alloy has the minimum FCP rate，followed by T3；（T3 135℃/60h）aging treatment has a slightly slower fatigue crack propagation rate than （T3 135℃/120h）;T6 temper has the maximum FCP rate. Aging conditions have a significant influence on the FCP in low ΔK level，but not in high ΔK level. The δ?and fine T1 phases can enable slip planarity so as to enhance the reversibility of cyclic slip and reduce damage accumulation and stress intensity around the crack tip；slip planarity can also lead to the deflection of crack path and promote the crack closure effect.All these things result in an improvement of crack propagation resistance.Coarse and intensive T1 phase and semi-coherent θ?restrain slip planarity and easily induces stress intensity which can reduce crack propagation resistance.The Precipitation free zone(PFZ) and equilibrium phases at grain boundaries dramaticly reduce the strength of grain boundaries and lead to intergranular fracture ；this arouses greatly improvement in fatigue crack propagation rate.
2016, 45(12):3325-3329.
Abstract:
A nitride layer was first formed on Cr12MoV steel samples by plasma nitriding and then a CrNiTiN coating was prepared on the surface of nitrided and non-nitrided Cr12MoV steels using closed field unbalanced magnetron sputter ion plating. The coatings were characterized in terms of their structure , adhesion strength and abrasion resistance were compared between nitrided and non-nitrided Cr12MoV.The surface free energy of the coatings was calculated using the Qwens-Wendt geometric mean approach. The experimental results indicated that both low total surface energy (11.22mN/m) and poor adhesion strength (43N) could be obtained in the CrNiTiN coating. The high adhesive strength was achieved when Cr12MoV steel was treated with plasma nitriding , leading to the enhanced load strength between CrNiTiN films and substrate. The friction coefficient and wear rate of CrNiTiN coatings on plasma nitriding treated Cr12MoV steel substrate is far less than that of untreated one .The duplex treatment of plasma nitridation and CrNiTiN coatings could increase the total surface energy.
A nitride layer was first formed on Cr12MoV steel samples by plasma nitriding and then a CrNiTiN coating was prepared on the surface of nitrided and non-nitrided Cr12MoV steels using closed field unbalanced magnetron sputter ion plating. The coatings were characterized in terms of their structure , adhesion strength and abrasion resistance were compared between nitrided and non-nitrided Cr12MoV.The surface free energy of the coatings was calculated using the Qwens-Wendt geometric mean approach. The experimental results indicated that both low total surface energy (11.22mN/m) and poor adhesion strength (43N) could be obtained in the CrNiTiN coating. The high adhesive strength was achieved when Cr12MoV steel was treated with plasma nitriding , leading to the enhanced load strength between CrNiTiN films and substrate. The friction coefficient and wear rate of CrNiTiN coatings on plasma nitriding treated Cr12MoV steel substrate is far less than that of untreated one .The duplex treatment of plasma nitridation and CrNiTiN coatings could increase the total surface energy.
2016, 45(12):3330-3334.
Abstract:
Zr-4 alloys thick walled pipes are the important parts in nuclear power station fuel supply system, its processing capacity can be reduced through three points straightening after extrusion. The micro stress and strain variation during pipe elastic deformation, elastic-plastic deformation, and rebound deformation had been analyzed based on elastic-plastic theory, and built the M-?-? equation, which can express the relation between elastic-plastic bending deformation and unloading procedure. The Zr-4 alloys thick walled pipes elastic -linear hardening constitutive model had been built based on material characteristics to computer the straitening deformation and proposed a straightening stroke algorithm of Zr-4 alloys thick walled pipe. Several 5m length pipes with the maximum deformation more than 20mm, 6 detecting points had been used straightening experiment, and all of pipe’s straightness were less than 0.50mm and the straightening time reduced from 1.5h/pcs by hand-straightening to 22.5min/pcs automation, and the results indicate that the algorithm practical is good.
Zr-4 alloys thick walled pipes are the important parts in nuclear power station fuel supply system, its processing capacity can be reduced through three points straightening after extrusion. The micro stress and strain variation during pipe elastic deformation, elastic-plastic deformation, and rebound deformation had been analyzed based on elastic-plastic theory, and built the M-?-? equation, which can express the relation between elastic-plastic bending deformation and unloading procedure. The Zr-4 alloys thick walled pipes elastic -linear hardening constitutive model had been built based on material characteristics to computer the straitening deformation and proposed a straightening stroke algorithm of Zr-4 alloys thick walled pipe. Several 5m length pipes with the maximum deformation more than 20mm, 6 detecting points had been used straightening experiment, and all of pipe’s straightness were less than 0.50mm and the straightening time reduced from 1.5h/pcs by hand-straightening to 22.5min/pcs automation, and the results indicate that the algorithm practical is good.
2016, 45(12):3335-3340.
Abstract:
Alloy 718Plus is a recently developed Ni-Fe based superalloy that is capable of maintaining excellent strength, hot working and welding performance up to 704oC (1300oF). In this paper, the development of 718Plus alloy research in China was summarized. It mainly includes four sections. (1) The phase composition and structure of alloy 718plus, (2) The effect of phosphorus on microstructure and mechanical properties of alloy 718Plus, (3) The effect of aluminum on microstructure and mechanical properties of alloy ATI 718Plus, (4) The effect of η-Ni3Al0.5Nb0.5 phase on mechanical properties of alloy ATI 718Plus. Based on above research, we can have an insight into the structure of phases in alloy 718Plus and the mechanism of alloying elements on the alloy 718Plus.
Alloy 718Plus is a recently developed Ni-Fe based superalloy that is capable of maintaining excellent strength, hot working and welding performance up to 704oC (1300oF). In this paper, the development of 718Plus alloy research in China was summarized. It mainly includes four sections. (1) The phase composition and structure of alloy 718plus, (2) The effect of phosphorus on microstructure and mechanical properties of alloy 718Plus, (3) The effect of aluminum on microstructure and mechanical properties of alloy ATI 718Plus, (4) The effect of η-Ni3Al0.5Nb0.5 phase on mechanical properties of alloy ATI 718Plus. Based on above research, we can have an insight into the structure of phases in alloy 718Plus and the mechanism of alloying elements on the alloy 718Plus.
