Volume 38,Issue 8,2009 Table of Contents
2009, 38(8):1317-1320.
Abstract:
A 3D thermal elastic-plastic finite element model to predict welding residual stresses induced by full-penetration laser welding of Ti6Al4V alloy was described in detail. The welding experiments and residual stresses measurements by through-thickness hole-drilling method were also performed to validate the simulated results. A uniform conical heat source model with parameters taken from the actual weld seam dimensions was developed to simulate the welding temperature fields with different welding heat inputs. The thermal elastic-plastic finite element simulation was employed to calculate the welding residual stresses. The boundary conditions and the size of finite element mesh were also discussed. The results show that the cross section profiles of the weld seam simulated with the conical heat source based on the configuration of weld seam agree well with the experimental results; the zone of residual stresses distribution in laser full-penetration welding of Ti6Al4V alloy is very narrow and the gradient of longitudinal residual stress is very steep; the residual stresses distribution on the surfaces are different from those in the interior of the welding seam; the measured residual stresses by through-thickness hole-drilling method are similar to the simulated ones in the interior of the welding seam.
A 3D thermal elastic-plastic finite element model to predict welding residual stresses induced by full-penetration laser welding of Ti6Al4V alloy was described in detail. The welding experiments and residual stresses measurements by through-thickness hole-drilling method were also performed to validate the simulated results. A uniform conical heat source model with parameters taken from the actual weld seam dimensions was developed to simulate the welding temperature fields with different welding heat inputs. The thermal elastic-plastic finite element simulation was employed to calculate the welding residual stresses. The boundary conditions and the size of finite element mesh were also discussed. The results show that the cross section profiles of the weld seam simulated with the conical heat source based on the configuration of weld seam agree well with the experimental results; the zone of residual stresses distribution in laser full-penetration welding of Ti6Al4V alloy is very narrow and the gradient of longitudinal residual stress is very steep; the residual stresses distribution on the surfaces are different from those in the interior of the welding seam; the measured residual stresses by through-thickness hole-drilling method are similar to the simulated ones in the interior of the welding seam.
2009, 38(8):1321-1324.
Abstract:
The finite element model, which considered the interfacial reaction layer was developed to evaluate interfacial shear strength of titanium matrix composites (TMCs) and analyze the effect of interface reaction on interfacial mechanical properties. The results show that the interfacial shear strength of SiC/Timetal-834 evaluated is about 500 MPa, and that the interfacial shear strength increases as the interfacial reaction enhances. Moreover, the relationship between the thickness of the interfacial reaction layer and the interfacial shear strength is built.
The finite element model, which considered the interfacial reaction layer was developed to evaluate interfacial shear strength of titanium matrix composites (TMCs) and analyze the effect of interface reaction on interfacial mechanical properties. The results show that the interfacial shear strength of SiC/Timetal-834 evaluated is about 500 MPa, and that the interfacial shear strength increases as the interfacial reaction enhances. Moreover, the relationship between the thickness of the interfacial reaction layer and the interfacial shear strength is built.
2009, 38(8):1325-1327.
Abstract:
The effects of the annealing time on the microstructure and magnetic properties of Dy0.5Fe60Pt39. 5 were investigated. X-ray diffraction and M-T data indicated that the disordered face-centered-cubic phase (soft phase) is not truly disordered phase due to an increase in the degree of short-range order with increasing of annealing time. Both the coercivity and remanence ratio of the FePt based alloy are as a function of the annealing time. The optimum heat treatment condition for the alloy is at annealing temperature of 600 °C for 5 h. These results of magnetic properties can be explained on the basis of phase transformation and microstructure of the alloy.
The effects of the annealing time on the microstructure and magnetic properties of Dy0.5Fe60Pt39. 5 were investigated. X-ray diffraction and M-T data indicated that the disordered face-centered-cubic phase (soft phase) is not truly disordered phase due to an increase in the degree of short-range order with increasing of annealing time. Both the coercivity and remanence ratio of the FePt based alloy are as a function of the annealing time. The optimum heat treatment condition for the alloy is at annealing temperature of 600 °C for 5 h. These results of magnetic properties can be explained on the basis of phase transformation and microstructure of the alloy.
2009, 38(8):1328-1332.
Abstract:
The effects of additives Ti and LaCl3 on the hydrogen storage properties of NaAlH4 and LiAlH4 were investigated by the PCT (pressure-content-temperature) apparatus. NaAlH4 doped with LaCl3 and LiAlH4 doped with LaCl3 both show better capability of hydrogen release than the samples doped with Ti. The study on the first rehydrogenation cycle of NaAlH4 doped with 3 mol% LaCl3 finds that the dehydrogenation temperature has a marked decrease. In addition, the effect of LaCl3 content on hydrogen release of NaAlH4 is very obvious. The result indicates that the amount and rate of hydrogen release show the same change trends, increasing firstly and then decreasing with increasing of LaCl3 content. The sample doped with 3 mol% LaCl3 presents the best dehydrogenation properties in both the amount of hydrogen release and the desorption kinetics. The activation energy of the NaAlH4 sample doped with 3 mol% LaCl3 was measured to be 41.6 kJ/mol. This value is lower than that reported for the Ti-doped NaAlH4.
The effects of additives Ti and LaCl3 on the hydrogen storage properties of NaAlH4 and LiAlH4 were investigated by the PCT (pressure-content-temperature) apparatus. NaAlH4 doped with LaCl3 and LiAlH4 doped with LaCl3 both show better capability of hydrogen release than the samples doped with Ti. The study on the first rehydrogenation cycle of NaAlH4 doped with 3 mol% LaCl3 finds that the dehydrogenation temperature has a marked decrease. In addition, the effect of LaCl3 content on hydrogen release of NaAlH4 is very obvious. The result indicates that the amount and rate of hydrogen release show the same change trends, increasing firstly and then decreasing with increasing of LaCl3 content. The sample doped with 3 mol% LaCl3 presents the best dehydrogenation properties in both the amount of hydrogen release and the desorption kinetics. The activation energy of the NaAlH4 sample doped with 3 mol% LaCl3 was measured to be 41.6 kJ/mol. This value is lower than that reported for the Ti-doped NaAlH4.
2009, 38(8):1333-1337.
Abstract:
The microstructures of as-SHSed Stellite 6 and as-cast HS111 were investigated by SEM, XRD and EPMA. It was shown that there is significant similarity in the microstructures of as-SHSed Stellite 6 and as-cast HS111. But carbides of continuous cast HS111 alloy can form single and uniform carbides phase.
The microstructures of as-SHSed Stellite 6 and as-cast HS111 were investigated by SEM, XRD and EPMA. It was shown that there is significant similarity in the microstructures of as-SHSed Stellite 6 and as-cast HS111. But carbides of continuous cast HS111 alloy can form single and uniform carbides phase.
2009, 38(8):1338-1342.
Abstract:
The hot deformation behaviors of TiC particle-reinforced Ti matrix composites were studied at the temperature range of 900~1150 ℃ and the strain rate range of 0.001~10 s-1 on the Gleeble-1500 simulator by the hot compression test. On the basis of the obtained stress-strain curves, the hot deformation characteristics of the alloys were analyzed; the average deformation activation energy of 799 kJ/mol in the (α+β) region and 105 kJ/mol in the β region were calculated using kinetic rate equation, and the processing map for hot working was established based on the kinetic model. The high-power dissipation region and flow instability region in the processing map were analyzed. The deformation mechanism of different regions in the processing map was determined and the microstructure evolution after deformation was observed and studied. The results show that superplastic deformation and dynamic recrystallization was observed at 900~980 ℃ and 0.001~0.1 s-1; the leading deformation mechanism is dynamic recrystallization which controlled by sub-boundary migration and diffusion at 1000~1100 ℃ and 0.1~10 s-1; and the two flow instability regions appeared at the temperature range of 900~950 ℃ and strain rate range of 0.1~10 s-1 and the temperature range of 1080~1130 ℃ and strain rate range of 0.001~0.01 s-1 according to the processing map.
The hot deformation behaviors of TiC particle-reinforced Ti matrix composites were studied at the temperature range of 900~1150 ℃ and the strain rate range of 0.001~10 s-1 on the Gleeble-1500 simulator by the hot compression test. On the basis of the obtained stress-strain curves, the hot deformation characteristics of the alloys were analyzed; the average deformation activation energy of 799 kJ/mol in the (α+β) region and 105 kJ/mol in the β region were calculated using kinetic rate equation, and the processing map for hot working was established based on the kinetic model. The high-power dissipation region and flow instability region in the processing map were analyzed. The deformation mechanism of different regions in the processing map was determined and the microstructure evolution after deformation was observed and studied. The results show that superplastic deformation and dynamic recrystallization was observed at 900~980 ℃ and 0.001~0.1 s-1; the leading deformation mechanism is dynamic recrystallization which controlled by sub-boundary migration and diffusion at 1000~1100 ℃ and 0.1~10 s-1; and the two flow instability regions appeared at the temperature range of 900~950 ℃ and strain rate range of 0.1~10 s-1 and the temperature range of 1080~1130 ℃ and strain rate range of 0.001~0.01 s-1 according to the processing map.
2009, 38(8):1343-1347.
Abstract:
The non-isothermal crystallization kinetics of Fe41Co7Cr15Mo14Y2C15B6 bulk amorphous alloy with high glass forming ability was studied by the differential thermal analyzer (DTA). Glass transition temperature Tg, onset crystallization temperature Tx and peak crystallization temperature Tp1 and Tp2 were obtained from DTA curves. These characteristic temperatures were of obvious dynamic effect. The glass transition activation energy Eg, crystallization activation energy Ex, and activation energy Ep1, Ep2 corresponding to characteristic temperatures Tg, Tx, Tp1, Tp2 were calculated by Kissinger and Ozawa equations, respectively. The thermodynamics mechanism of Fe41Co7Cr15Mo14Y2C15B6 bulk amorphous alloy with high thermal stability was explained by Kissinger method and Ozawa method.
The non-isothermal crystallization kinetics of Fe41Co7Cr15Mo14Y2C15B6 bulk amorphous alloy with high glass forming ability was studied by the differential thermal analyzer (DTA). Glass transition temperature Tg, onset crystallization temperature Tx and peak crystallization temperature Tp1 and Tp2 were obtained from DTA curves. These characteristic temperatures were of obvious dynamic effect. The glass transition activation energy Eg, crystallization activation energy Ex, and activation energy Ep1, Ep2 corresponding to characteristic temperatures Tg, Tx, Tp1, Tp2 were calculated by Kissinger and Ozawa equations, respectively. The thermodynamics mechanism of Fe41Co7Cr15Mo14Y2C15B6 bulk amorphous alloy with high thermal stability was explained by Kissinger method and Ozawa method.
2009, 38(8):1348-1352.
Abstract:
Surface irradiation for refractory Ni-based alloy DZ4 was realized by high intensity pulsed ion beam (HIPIB) containing Cn+ (30 mol%) and H+ (70 mol%), with pulse duration of 70 ns and current density of 100 A/cm2, under the accelerating voltage of 250 kV; while the treating pulses were chosen as 5, 10 and 15 times. The surface microstructure changes before and after irradiation was analyzed by TEM. Results show that compared with the original sample, a polycrystal layer appeared on the topmost surface of the sample, no matter what times it was irradiated; the layer was composed of Ni, Cr, Al, Ti, W, Mo and Co elemental crystal with grain size of 5~10 nm. g ￠ phase did not exist below the polycrystal layer in certain depth, but its content increased gradually as the depth increasing.
Surface irradiation for refractory Ni-based alloy DZ4 was realized by high intensity pulsed ion beam (HIPIB) containing Cn+ (30 mol%) and H+ (70 mol%), with pulse duration of 70 ns and current density of 100 A/cm2, under the accelerating voltage of 250 kV; while the treating pulses were chosen as 5, 10 and 15 times. The surface microstructure changes before and after irradiation was analyzed by TEM. Results show that compared with the original sample, a polycrystal layer appeared on the topmost surface of the sample, no matter what times it was irradiated; the layer was composed of Ni, Cr, Al, Ti, W, Mo and Co elemental crystal with grain size of 5~10 nm. g ￠ phase did not exist below the polycrystal layer in certain depth, but its content increased gradually as the depth increasing.
2009, 38(8):1353-1357.
Abstract:
The indentation creep behaviour of Sn-3.5Ag-2Bi-0.7Cu lead-free solder was studied in the temperature range of 50-100 ℃ and indentation stress range of 16.7-43.2 MPa. The stress exponent n of 3.181, creep activation energy Q of 59.189 kJ/mol, and material structural constant A of 0.423 were obtained. The constitutive equation of the steady state indentation creep rate of the Sn-3.5Ag-2Bi-0.7Cu lead-free solder was =0.423σ3.181exp(–59189/RT). The experiment shows that the indentation creep rate increased dramatically as the temperature and stress increased. The Ag3Sn and Cu6Sn5 phases became coarser and shorter after indentation creep, which could increase indentation creep resisting property by strengthening β-Sn matrix.
The indentation creep behaviour of Sn-3.5Ag-2Bi-0.7Cu lead-free solder was studied in the temperature range of 50-100 ℃ and indentation stress range of 16.7-43.2 MPa. The stress exponent n of 3.181, creep activation energy Q of 59.189 kJ/mol, and material structural constant A of 0.423 were obtained. The constitutive equation of the steady state indentation creep rate of the Sn-3.5Ag-2Bi-0.7Cu lead-free solder was =0.423σ3.181exp(–59189/RT). The experiment shows that the indentation creep rate increased dramatically as the temperature and stress increased. The Ag3Sn and Cu6Sn5 phases became coarser and shorter after indentation creep, which could increase indentation creep resisting property by strengthening β-Sn matrix.
2009, 38(8):1358-1362.
Abstract:
Hot deformation characteristics of molybdenum was investigated by hot compression tests carried out in the temperature range of 900-1450 °C and strain rate range of 0.01-10 s-1. A constitutive equation of hot deformation of molybdenum based on the flow stress was established. With consideration of the effects of the deformation temperatures and the stain rates on microstructures and properties of molybdenum, processing maps were established based on the dynamic material model (DMM). And the instability zones of flow behavior could also be recognized by the maps. The hot deformation characteristics of molybdenum in different zones were also analyzed.
Hot deformation characteristics of molybdenum was investigated by hot compression tests carried out in the temperature range of 900-1450 °C and strain rate range of 0.01-10 s-1. A constitutive equation of hot deformation of molybdenum based on the flow stress was established. With consideration of the effects of the deformation temperatures and the stain rates on microstructures and properties of molybdenum, processing maps were established based on the dynamic material model (DMM). And the instability zones of flow behavior could also be recognized by the maps. The hot deformation characteristics of molybdenum in different zones were also analyzed.
11 Study on Chemical Deposition of Calcium Phosphate Bioceramic Coating on AZ31 Magnesium Alloy Surface
2009, 38(8):1363-1367.
Abstract:
The preparation possibility of the calcium phosphate (Ca-P) bioceramic coating on AZ31 magnesium alloy treated by pre-calcification (pre-Ca) and the anodized oxidation process in Hank’s solutions and a mixed solution of Ca(NO3)2 and NH4H2PO4 (Ca-P solution) was investigated. The chemical composition and phase composition of the coating were analyzed by EDS and XRD. Results indicate that any coating on the AZ31 alloy treated by the above two pre-treatments could not be obtained in Hank’s solutions, whereas Ca-P coatings on the same substrates were acquired after the alloys were immersed in Ca-P solutions for 48 h. It was confirmed that this coating consisted of Brushite (CaHPO4·2H2O) and minor Ca(H2PO4)2. Ca nucleation site appeared on the surface of AZ31 alloy after pre-Ca treatment, and the deposited coatings in Ca-P solutions were uniform and compact. They were composed of flake-like crystals with 20~50 μm length and width, which interlaced each other. On the contrary, the coatings on the alloy treated by anodized oxidation in Ca-P solutions were leaf-like and not compact.
The preparation possibility of the calcium phosphate (Ca-P) bioceramic coating on AZ31 magnesium alloy treated by pre-calcification (pre-Ca) and the anodized oxidation process in Hank’s solutions and a mixed solution of Ca(NO3)2 and NH4H2PO4 (Ca-P solution) was investigated. The chemical composition and phase composition of the coating were analyzed by EDS and XRD. Results indicate that any coating on the AZ31 alloy treated by the above two pre-treatments could not be obtained in Hank’s solutions, whereas Ca-P coatings on the same substrates were acquired after the alloys were immersed in Ca-P solutions for 48 h. It was confirmed that this coating consisted of Brushite (CaHPO4·2H2O) and minor Ca(H2PO4)2. Ca nucleation site appeared on the surface of AZ31 alloy after pre-Ca treatment, and the deposited coatings in Ca-P solutions were uniform and compact. They were composed of flake-like crystals with 20~50 μm length and width, which interlaced each other. On the contrary, the coatings on the alloy treated by anodized oxidation in Ca-P solutions were leaf-like and not compact.
2009, 38(8):1368-1372.
Abstract:
Thermo-mechanical processing parameters of Ti-43Al-5Nb-0.03Y (mole fraction, %) alloy are investigated by hot simulation tests at 1050~1250 ℃ on Gleeble-1500D with a nominal deformation of 50% and a strain rate of 10-1~10-3?s-1. The true strain–true stress curves have been obtained and the microstructures are observed. The results show that the microstructure consists of recrystallized grains and remained-lamellar when the compression temperature is lower than 1200 ℃, and of recrystallized grains at 1200 ℃. The major mechanism of plastic deformation is the slip deformation and twinning deformation, and the main softening mechanism is dynamic the recrystallization and dynamic recovery in the γ phase. The crack-free pancakes are obtained at a hot compressive temperature of 1200 ℃ and a strain rate of 10-3 s-1.
Thermo-mechanical processing parameters of Ti-43Al-5Nb-0.03Y (mole fraction, %) alloy are investigated by hot simulation tests at 1050~1250 ℃ on Gleeble-1500D with a nominal deformation of 50% and a strain rate of 10-1~10-3?s-1. The true strain–true stress curves have been obtained and the microstructures are observed. The results show that the microstructure consists of recrystallized grains and remained-lamellar when the compression temperature is lower than 1200 ℃, and of recrystallized grains at 1200 ℃. The major mechanism of plastic deformation is the slip deformation and twinning deformation, and the main softening mechanism is dynamic the recrystallization and dynamic recovery in the γ phase. The crack-free pancakes are obtained at a hot compressive temperature of 1200 ℃ and a strain rate of 10-3 s-1.
2009, 38(8):1373-1377.
Abstract:
The CuxBy alloy and amorphous Mg50Ni50 hydrogen storage alloy were synthesized by mechanical alloying method (MA). And then surface modification of the amorphous Mg50Ni50 alloy was done using CuxBy by the same method. Effects of CuxBy with different composition and different doping ratio of CuxBy (the same composition) on the cycle stability of Mg50Ni50 alloy electrode were investigated. Results show that the surface modification through CuxBy with different composition can increase the cycle stability of Mg50Ni50 alloy electrode to different extent. However, the surface modification effects of CuxBy with the same composition but different doping ratio on the cycle stability of Mg50Ni50 alloy electrode have obvious difference. When Mg50Ni50:Cu0.9B0.1=5:1, the initial discharge capacity was 465 mAh·g-1, and the 50th one was 222 mAh·g-1. On the condition of keeping high discharge capacity, the cycle stability of amorphous Mg50Ni50 alloy was improved effectively.
The CuxBy alloy and amorphous Mg50Ni50 hydrogen storage alloy were synthesized by mechanical alloying method (MA). And then surface modification of the amorphous Mg50Ni50 alloy was done using CuxBy by the same method. Effects of CuxBy with different composition and different doping ratio of CuxBy (the same composition) on the cycle stability of Mg50Ni50 alloy electrode were investigated. Results show that the surface modification through CuxBy with different composition can increase the cycle stability of Mg50Ni50 alloy electrode to different extent. However, the surface modification effects of CuxBy with the same composition but different doping ratio on the cycle stability of Mg50Ni50 alloy electrode have obvious difference. When Mg50Ni50:Cu0.9B0.1=5:1, the initial discharge capacity was 465 mAh·g-1, and the 50th one was 222 mAh·g-1. On the condition of keeping high discharge capacity, the cycle stability of amorphous Mg50Ni50 alloy was improved effectively.
2009, 38(8):1378-1381.
Abstract:
The magnetic behavior of Gd1-xVx alloys (x=0.01, 0.03, 0.05, 0.07, 0.09) prepared by vacuum arc melting was analyzed. X-ray diffraction patterns show that all Gd1-xVx alloys retain crystal hexagonal structure of pure Gd. The ferromagnetic to paramagnetic phase transition of all alloys is the second order type. The Curie temperatures of these alloys are lower than that of Gd by 1~2 K and change a little with x increasing. It is noted that these alloys have large values of magnetic entropy change ΔSM, adiabatic temperatures change ΔTad and broader peak in the ΔSM-T plot in the low magnetic fields. All the alloys have remarkably better relative cooling power than pure Gd.
The magnetic behavior of Gd1-xVx alloys (x=0.01, 0.03, 0.05, 0.07, 0.09) prepared by vacuum arc melting was analyzed. X-ray diffraction patterns show that all Gd1-xVx alloys retain crystal hexagonal structure of pure Gd. The ferromagnetic to paramagnetic phase transition of all alloys is the second order type. The Curie temperatures of these alloys are lower than that of Gd by 1~2 K and change a little with x increasing. It is noted that these alloys have large values of magnetic entropy change ΔSM, adiabatic temperatures change ΔTad and broader peak in the ΔSM-T plot in the low magnetic fields. All the alloys have remarkably better relative cooling power than pure Gd.
2009, 38(8):1382-1385.
Abstract:
CuCo catalysts used for synthesis of low-carbon alcohol by CO+H2 were prepared by the reverse coprecipitation method under the ultrasound irradiation. The influence of rare earth Ce assistant on the structure and catalytic properties was investigated. The experimental catalysts were extensively characterized by XRD, BET, TPR and TPD techniques. It was found that after the addition of rare earth Ce, the crystallite size of the catalytic material was decreased, the reducibility was enhanced, the specific surface area was increased and the formation of the active sites for alcohols was improved significantly. Therefore, the activity and selectivity of the rare earth promoted catalyst were improved remarkably.
CuCo catalysts used for synthesis of low-carbon alcohol by CO+H2 were prepared by the reverse coprecipitation method under the ultrasound irradiation. The influence of rare earth Ce assistant on the structure and catalytic properties was investigated. The experimental catalysts were extensively characterized by XRD, BET, TPR and TPD techniques. It was found that after the addition of rare earth Ce, the crystallite size of the catalytic material was decreased, the reducibility was enhanced, the specific surface area was increased and the formation of the active sites for alcohols was improved significantly. Therefore, the activity and selectivity of the rare earth promoted catalyst were improved remarkably.
2009, 38(8):1386-1389.
Abstract:
Insufficient bond strength between ceramic and titanium restricts their application in clinic. The attempt of the present study is made to introduce a concept of the titanium alloy with low elastic modulus for simulating and investigating different destroying conditions such as shear load at metal-ceramic interface, middle bending load etc. The results indicate that the interface stress level of titanium alloy with low elastic modulus is 6% lower than that of pure titanium when the alloy is subjected to shear load. On the condition of being subjected to middle bending load, the thickness of titanium alloy substrates of low elastic modulus should be increased to obtain better match between stiffness and stress distribution, which could be well satisfied in clinic (thickness>2 mm).
Insufficient bond strength between ceramic and titanium restricts their application in clinic. The attempt of the present study is made to introduce a concept of the titanium alloy with low elastic modulus for simulating and investigating different destroying conditions such as shear load at metal-ceramic interface, middle bending load etc. The results indicate that the interface stress level of titanium alloy with low elastic modulus is 6% lower than that of pure titanium when the alloy is subjected to shear load. On the condition of being subjected to middle bending load, the thickness of titanium alloy substrates of low elastic modulus should be increased to obtain better match between stiffness and stress distribution, which could be well satisfied in clinic (thickness>2 mm).
2009, 38(8):1390-1393.
Abstract:
The evolutions of grain boundary orientation differential of TA15 alloy after annealing heat treatments at different temperatures were investigated by EBSD and TEM. The results show a few small-angle grain boundaries of TA15 alloy transformed into large-angle grain boundaries when annealed at 800 ℃; more grain boundaries with large angle appeared greatly while annealed at 950 ℃; the average thermal activation energy was 151.4 kJ/mol for the transformation from small-angle grain boundaries to large angle grain boundaries, which is equal to the self-diffusion activation energy of α-Ti; it means that the transformation from the small-angle grain boundaries to the large-angle boundaries was controlled by the self-diffusion of titanium atoms. TEM micrographs show sub grain boundaries transformed into dislocation net with hexagonal net at the annealing temperature of 800 ℃, while lots of equiaxed grains were obtained after annealing treatment at 950 ℃.
The evolutions of grain boundary orientation differential of TA15 alloy after annealing heat treatments at different temperatures were investigated by EBSD and TEM. The results show a few small-angle grain boundaries of TA15 alloy transformed into large-angle grain boundaries when annealed at 800 ℃; more grain boundaries with large angle appeared greatly while annealed at 950 ℃; the average thermal activation energy was 151.4 kJ/mol for the transformation from small-angle grain boundaries to large angle grain boundaries, which is equal to the self-diffusion activation energy of α-Ti; it means that the transformation from the small-angle grain boundaries to the large-angle boundaries was controlled by the self-diffusion of titanium atoms. TEM micrographs show sub grain boundaries transformed into dislocation net with hexagonal net at the annealing temperature of 800 ℃, while lots of equiaxed grains were obtained after annealing treatment at 950 ℃.
2009, 38(8):1394-1397.
Abstract:
Based on the study of W-Y2O3 metallization process of Al2O3 (including 95% Al2O3 ceramic and Al2O3 single crystal), the high-temperature brazing joints of single crystal Al2O3/Pd/Nb were fabricated. W-Y2O3 metallization mechanism of Al2O3 and Pd brazing mechanism of Al2O3/Nb were analyzed. The results show that there was aggregation behavior of Y near the interface between the Al2O3 substrate and metallizing layer; meanwhile Al content decreased. This resulted from the diffusion of some new solid phase products at the interface of ceramic/metallizing layer during metallization. The diffusion direction was mainly towards the metallizing layer. The W and Nb elements nearly diffused into the whole Pd brazing interlayer during high-temperature brazing, which led to forming of brittle solid solutions or intermetallic compounds in the solder layer and near Nb/Pd interface, resulting in micro-cracks.
Based on the study of W-Y2O3 metallization process of Al2O3 (including 95% Al2O3 ceramic and Al2O3 single crystal), the high-temperature brazing joints of single crystal Al2O3/Pd/Nb were fabricated. W-Y2O3 metallization mechanism of Al2O3 and Pd brazing mechanism of Al2O3/Nb were analyzed. The results show that there was aggregation behavior of Y near the interface between the Al2O3 substrate and metallizing layer; meanwhile Al content decreased. This resulted from the diffusion of some new solid phase products at the interface of ceramic/metallizing layer during metallization. The diffusion direction was mainly towards the metallizing layer. The W and Nb elements nearly diffused into the whole Pd brazing interlayer during high-temperature brazing, which led to forming of brittle solid solutions or intermetallic compounds in the solder layer and near Nb/Pd interface, resulting in micro-cracks.
2009, 38(8):1398-1401.
Abstract:
The brazing experiments of CBN abrasive grains and the steel with 0.45%C using Ag-Cu-Ti alloy reinforced by TiN particles as composite filler were carried out with heating temperature of 920 ℃ and dwell time of 5 min. The interfacial microstructure and characteristics among TiN particles, Ag-Cu-Ti alloy, CBN grains and the steel substrate were detected with three-dimensional video microscope, scanning electron microscope (SEM), energy dispersion spectrometer (EDS) and X-ray diffraction (XRD). The results show that the microstructure of Ag-Cu-Ti alloy is refined obviously by the well-dispersive TiN particles. The interfacial zone between the particles and the filler is uniformity and compact, and the microhardness of the filler layer is improved. Good combination between the filler and the substrate can still be obtained when the TiN particles are applied. The composite filler doesn’t take negative effects upon the chemical reaction between CBN grains and the filler. Good wetting ability of the composite filler is realized on the CBN grains during brazing, which ensure the hard join to the grains.
The brazing experiments of CBN abrasive grains and the steel with 0.45%C using Ag-Cu-Ti alloy reinforced by TiN particles as composite filler were carried out with heating temperature of 920 ℃ and dwell time of 5 min. The interfacial microstructure and characteristics among TiN particles, Ag-Cu-Ti alloy, CBN grains and the steel substrate were detected with three-dimensional video microscope, scanning electron microscope (SEM), energy dispersion spectrometer (EDS) and X-ray diffraction (XRD). The results show that the microstructure of Ag-Cu-Ti alloy is refined obviously by the well-dispersive TiN particles. The interfacial zone between the particles and the filler is uniformity and compact, and the microhardness of the filler layer is improved. Good combination between the filler and the substrate can still be obtained when the TiN particles are applied. The composite filler doesn’t take negative effects upon the chemical reaction between CBN grains and the filler. Good wetting ability of the composite filler is realized on the CBN grains during brazing, which ensure the hard join to the grains.
2009, 38(8):1402-1405.
Abstract:
The change and its mechanism of the infrared emissivity of superalloy K424 with deposited Au film before and after heat treatment were investigated. XRD analyses show that the metal elements of the substrate diffused from the alloy into the Au film, and mainly formed the solid solution of Cr in Au, i.e. Au0.7Cr0.3. EDXS analyses show that oxides of substrate metal element were formed on the rough surface of the sample with deposited Au film after heat treatment; while the polished surface of the sample was still Au film. Both the surface state and heat treatment have great influence on the infrared emissivity tested by spectral radiometer, SR5000.
The change and its mechanism of the infrared emissivity of superalloy K424 with deposited Au film before and after heat treatment were investigated. XRD analyses show that the metal elements of the substrate diffused from the alloy into the Au film, and mainly formed the solid solution of Cr in Au, i.e. Au0.7Cr0.3. EDXS analyses show that oxides of substrate metal element were formed on the rough surface of the sample with deposited Au film after heat treatment; while the polished surface of the sample was still Au film. Both the surface state and heat treatment have great influence on the infrared emissivity tested by spectral radiometer, SR5000.
2009, 38(8):1406-1409.
Abstract:
The mineralization ability of 4 kinds of titanium implants after chemical and bionic modification was evaluated. The 4 kinds of surface modification layers were anatase nanotubes (N), micro/nanostructure (MN), nanotubes with grafted Arg-Gly-Asp-Cys (NR), micro/nanostructure with grafted Arg-Gly-Asp-Cys (MNR). Results show that the surface mineralization deposition is hydroxylapatite. Under the same condition, the inducing mineralization ability of the samples is MNR>MN>NR>N. Combination of developing micro/nanostructure and grafting polypeptide is an effective way of surface modification for biomaterials.
The mineralization ability of 4 kinds of titanium implants after chemical and bionic modification was evaluated. The 4 kinds of surface modification layers were anatase nanotubes (N), micro/nanostructure (MN), nanotubes with grafted Arg-Gly-Asp-Cys (NR), micro/nanostructure with grafted Arg-Gly-Asp-Cys (MNR). Results show that the surface mineralization deposition is hydroxylapatite. Under the same condition, the inducing mineralization ability of the samples is MNR>MN>NR>N. Combination of developing micro/nanostructure and grafting polypeptide is an effective way of surface modification for biomaterials.
2009, 38(8):1410-1413.
Abstract:
amorphous alloy; crystallization kinetics; activation energy; thermal stability
amorphous alloy; crystallization kinetics; activation energy; thermal stability
2009, 38(8):1414-1417.
Abstract:
The sub-eutectoid U-Nb alloy tube was spun with reduction ratio of 15% at room temperature. The samples sectioned from the spun tube were annealed at 700, 655 and 600 ℃ in the vacuum for 1 h, respectively. The effects of cold-spinning and different temperature annealing on the microstructure evolution were studied by means of optical metallography(OM), scanning electron microscopy(SEM) and X-ray diffraction (XRD). The results indicate that cold-spinning deformation can refine the initial microstructure by mechanical breaking. The alloy after different-temperature annealing had different α+γ binary phase pealite microstructure, i.e. particle-like at 600 ℃, layer-like at 655 ℃ and stick-like at 700 ℃.
The sub-eutectoid U-Nb alloy tube was spun with reduction ratio of 15% at room temperature. The samples sectioned from the spun tube were annealed at 700, 655 and 600 ℃ in the vacuum for 1 h, respectively. The effects of cold-spinning and different temperature annealing on the microstructure evolution were studied by means of optical metallography(OM), scanning electron microscopy(SEM) and X-ray diffraction (XRD). The results indicate that cold-spinning deformation can refine the initial microstructure by mechanical breaking. The alloy after different-temperature annealing had different α+γ binary phase pealite microstructure, i.e. particle-like at 600 ℃, layer-like at 655 ℃ and stick-like at 700 ℃.
2009, 38(8):1418-1421.
Abstract:
Ta-W-Hf dense alloy material with continuous cellular strengthening structure was produced by powder metallurgy (PM) method. The plastic deformation characteristic of the high-strength material was researched by compression test to find out the possibility of further deformation process. The results indicate that the compression deformation characteristics of Ta-W-Hf alloy with continuous cellular strengthening structure were similar to that of the traditional material. Both of them can be subjected to cold compressed deformation with larger than 50% deformation amount but without macroscopical crack. The hardness of the sample was increased with deformation amount increasing. But the hardness increment of the sample annealed at high temperature was much larger than that of the HIPed sample. So the sample annealed at high temperature has much larger capacity of deformation strengthening.
Ta-W-Hf dense alloy material with continuous cellular strengthening structure was produced by powder metallurgy (PM) method. The plastic deformation characteristic of the high-strength material was researched by compression test to find out the possibility of further deformation process. The results indicate that the compression deformation characteristics of Ta-W-Hf alloy with continuous cellular strengthening structure were similar to that of the traditional material. Both of them can be subjected to cold compressed deformation with larger than 50% deformation amount but without macroscopical crack. The hardness of the sample was increased with deformation amount increasing. But the hardness increment of the sample annealed at high temperature was much larger than that of the HIPed sample. So the sample annealed at high temperature has much larger capacity of deformation strengthening.
2009, 38(8):1422-1425.
Abstract:
The mechanical properties at room and elevated temperature as well as the friction wear behavior under dry sliding condition for as-cast Mg97Zn1Y2 alloy were investigated, and compared with that of AZ91 alloy. The results show that the yield strength of AZ91 alloy is higher than that of Mg97Zn1Y2 alloy at room temperature, but Mg97Zn1Y2 alloy exhibits better thermal stability at the evaluated temperature; as the temperature is above 150 ℃, the yield strength of AZ91 alloy decreases sharply, but that of Mg97Zn1Y2 alloy decreases a little. The transition point from mild wear to severe wear for Mg97Zn1Y2 alloy obviously lags that of AZ91 alloy. In the same load range, the bulk temperature rise of wear surface of the Mg97Zn1Y2 alloy is also lower than that of AZ91 alloy. The reason is that the intermetallic compound Mg12YZn in Mg97Zn1Y2 alloy possesses better thermal stability than Mg17Al12 phase in AZ91 alloy.
The mechanical properties at room and elevated temperature as well as the friction wear behavior under dry sliding condition for as-cast Mg97Zn1Y2 alloy were investigated, and compared with that of AZ91 alloy. The results show that the yield strength of AZ91 alloy is higher than that of Mg97Zn1Y2 alloy at room temperature, but Mg97Zn1Y2 alloy exhibits better thermal stability at the evaluated temperature; as the temperature is above 150 ℃, the yield strength of AZ91 alloy decreases sharply, but that of Mg97Zn1Y2 alloy decreases a little. The transition point from mild wear to severe wear for Mg97Zn1Y2 alloy obviously lags that of AZ91 alloy. In the same load range, the bulk temperature rise of wear surface of the Mg97Zn1Y2 alloy is also lower than that of AZ91 alloy. The reason is that the intermetallic compound Mg12YZn in Mg97Zn1Y2 alloy possesses better thermal stability than Mg17Al12 phase in AZ91 alloy.
2009, 38(8):1426-1428.
Abstract:
The effect of Co addition on the density of states (DOS) distribution of Ni-Mn-Ga ferromagnetic shape memory alloys was investigated by first-principles plane-wave pseudo-potential method based on the density functional theory. The mechanism of effect of Co element on martensitic transformation of Ni-Mn-Ga alloy was clarified. Results show that with Co content increasing, more Co3d-Mn3d hybridization replaced Ni3d-Mn3d, improving parent phase stability and decreasing martensitic transformation temperature. In addition, it is noted that Co addition has little effect on majority-spin DOS of Ni-Mn-Ga-Co parent phase, but changes minority-spin DOS significantly.
The effect of Co addition on the density of states (DOS) distribution of Ni-Mn-Ga ferromagnetic shape memory alloys was investigated by first-principles plane-wave pseudo-potential method based on the density functional theory. The mechanism of effect of Co element on martensitic transformation of Ni-Mn-Ga alloy was clarified. Results show that with Co content increasing, more Co3d-Mn3d hybridization replaced Ni3d-Mn3d, improving parent phase stability and decreasing martensitic transformation temperature. In addition, it is noted that Co addition has little effect on majority-spin DOS of Ni-Mn-Ga-Co parent phase, but changes minority-spin DOS significantly.
2009, 38(8):1429-1431.
Abstract:
Element distribution of the bulk amorphous Zr41Ti14Cu12.5Ni10Be22.5 alloy and of the zone around the structural free volume in the undercooled liquid region was investigated by X-ray diffraction (XRD) and positron annihilation techniques(PAT)-Doppler broadening spectrum. Results show that the structural free volumes in the initially prepared Zr41Ti14Cu12.5Ni10Be22.5 alloy were mainly surrounded by Zr atoms. After the alloy was annealed at 400 ℃ in the undercooled liquid region, both atoms Ti and Be together with Zr were detected to surround the structural free volumes.
Element distribution of the bulk amorphous Zr41Ti14Cu12.5Ni10Be22.5 alloy and of the zone around the structural free volume in the undercooled liquid region was investigated by X-ray diffraction (XRD) and positron annihilation techniques(PAT)-Doppler broadening spectrum. Results show that the structural free volumes in the initially prepared Zr41Ti14Cu12.5Ni10Be22.5 alloy were mainly surrounded by Zr atoms. After the alloy was annealed at 400 ℃ in the undercooled liquid region, both atoms Ti and Be together with Zr were detected to surround the structural free volumes.
2009, 38(8):1432-1436.
Abstract:
Dynamic recrystallization behavior of Ti40 burn-resistant alloy, a highly stabilized β titanium alloy, was researched by hot compression test. The results indicate that the nucleation mechanism of dynamic recrystalization of Ti40 alloy includes subgrain nucleation, initial grain boundary bulging nucleation and dislocation pile-up nucleation. After high temperature plastic deformation, air-cooling and annealing at 850 ℃, the recrystallization grains of the alloy present mixed grain structure. Recrystallization grains grow sufficiently after the alloy is annealed at 1000 ℃, which is whole recrystallization structure.
Dynamic recrystallization behavior of Ti40 burn-resistant alloy, a highly stabilized β titanium alloy, was researched by hot compression test. The results indicate that the nucleation mechanism of dynamic recrystalization of Ti40 alloy includes subgrain nucleation, initial grain boundary bulging nucleation and dislocation pile-up nucleation. After high temperature plastic deformation, air-cooling and annealing at 850 ℃, the recrystallization grains of the alloy present mixed grain structure. Recrystallization grains grow sufficiently after the alloy is annealed at 1000 ℃, which is whole recrystallization structure.
2009, 38(8):1437-1440.
Abstract:
Near-equiatomic (Fe/Pd)n multilayer films were deposited on the surface of medical 316L stainless steel stents by vacuum arc ion plating technology. The crystal structure, morphology and component of (Fe/Pd)n multilayer films were studied by XRD, SEM, and electronic energy spectrum and the phase transformation was also analyzed. The magnetic performances of the samples were detected by CTCC-1 numeral magnetic flux and magnetic field measurement instrument. The results indicate that the optimum structure of superficial magnetic films on medical 316L steel stents is “Pd/Fe/Pd”. After diffusion heat treatment, (Fe/Pd)n films changed from face-center-cubic (fcc) structure to face-center-tetragonal (fct) structure. The film is uniform with high density and good bonding strength. At the same time, its effective magnetic strength is to up to 5×10-4 T for 6 months.
Near-equiatomic (Fe/Pd)n multilayer films were deposited on the surface of medical 316L stainless steel stents by vacuum arc ion plating technology. The crystal structure, morphology and component of (Fe/Pd)n multilayer films were studied by XRD, SEM, and electronic energy spectrum and the phase transformation was also analyzed. The magnetic performances of the samples were detected by CTCC-1 numeral magnetic flux and magnetic field measurement instrument. The results indicate that the optimum structure of superficial magnetic films on medical 316L steel stents is “Pd/Fe/Pd”. After diffusion heat treatment, (Fe/Pd)n films changed from face-center-cubic (fcc) structure to face-center-tetragonal (fct) structure. The film is uniform with high density and good bonding strength. At the same time, its effective magnetic strength is to up to 5×10-4 T for 6 months.
2009, 38(8):1441-1445.
Abstract:
Interfacial reactions between Ti-47Al alloy and crucible materials of Al2O3, ZrO2, and graphite during directional solidification process were investigated. By the OM and SEM observation of solidification microstructure, the interfacial reaction between TiAl alloy and Al2O3 crucible was serious, and a large number of α-Al2O3 inclusion formed in the solidification microstructure. The interfacial reaction between TiAl alloy and ZrO2 crucible occurred only on the sample surface, but the crucible was not stable at high temperature and a tack coating was formed, clinging tightly with TiAl alloy. C element in the graphite crucible changed the original solidification path of TiAl alloy, and club-shaped γ-TiAl phases formed.
Interfacial reactions between Ti-47Al alloy and crucible materials of Al2O3, ZrO2, and graphite during directional solidification process were investigated. By the OM and SEM observation of solidification microstructure, the interfacial reaction between TiAl alloy and Al2O3 crucible was serious, and a large number of α-Al2O3 inclusion formed in the solidification microstructure. The interfacial reaction between TiAl alloy and ZrO2 crucible occurred only on the sample surface, but the crucible was not stable at high temperature and a tack coating was formed, clinging tightly with TiAl alloy. C element in the graphite crucible changed the original solidification path of TiAl alloy, and club-shaped γ-TiAl phases formed.
2009, 38(8):1446-1449.
Abstract:
Citric acid chelating method was used to prepare Ce3+ doped BaHfO3 nano-powder. TG-DTA, XRD and SEM were employed to characterize the powder. The excitation and emission spectra of the specimens were analyzed by the fluorescence photometer. Results show that BaHfO3:Ce3+ nanometer powder with high degree of crystallinity, nearly spherical morphology and 40 nm particle size could be synthesized after the precursor gel prepared under the condition of CA:EG=1:3 was calcined at 1050 ℃ for 2 h. The maximum relative intensities of the excitation spectra and emission spectra appeared for the BaHfO3:Ce3+ specimen with Ce3+ doped concentration of 0.9 mol%. The excitation spectrum has two relatively wide spectrum bands where there are maximum peak values at the wavelength of 393 nm and 445 nm, respectively. The emission spectra at lex= 393 nm and lex=445 nm also have two spectrum bands where exist maximum peak values at 530 nm and 590 nm, respectively, corresponding to 5d→2F5/2 and 5d→2F7/2 transitions of Ce3+ cation, respectively. The emission spectra at 393 nm and 445 nm are obviously different, because the 4f ground State of Ce3+ cation is formed by two energy levels, with the energy difference of about 2000 cm-1.
Citric acid chelating method was used to prepare Ce3+ doped BaHfO3 nano-powder. TG-DTA, XRD and SEM were employed to characterize the powder. The excitation and emission spectra of the specimens were analyzed by the fluorescence photometer. Results show that BaHfO3:Ce3+ nanometer powder with high degree of crystallinity, nearly spherical morphology and 40 nm particle size could be synthesized after the precursor gel prepared under the condition of CA:EG=1:3 was calcined at 1050 ℃ for 2 h. The maximum relative intensities of the excitation spectra and emission spectra appeared for the BaHfO3:Ce3+ specimen with Ce3+ doped concentration of 0.9 mol%. The excitation spectrum has two relatively wide spectrum bands where there are maximum peak values at the wavelength of 393 nm and 445 nm, respectively. The emission spectra at lex= 393 nm and lex=445 nm also have two spectrum bands where exist maximum peak values at 530 nm and 590 nm, respectively, corresponding to 5d→2F5/2 and 5d→2F7/2 transitions of Ce3+ cation, respectively. The emission spectra at 393 nm and 445 nm are obviously different, because the 4f ground State of Ce3+ cation is formed by two energy levels, with the energy difference of about 2000 cm-1.
2009, 38(8):1450-1453.
Abstract:
A technology combining hot isostatic pressing (HIP) with isothermal forging (IF) was used to prepare TC17 powder alloy, and the changes of its microstructure and properties were also researched and analyzed. The results indicated that the powder alloy prepared by HIP of atomized TC17 powder with particle size <104 μm exhibited a homogeneous chemical composition and a fine acicular Widmanst?tten microstructure, and the tensile strength at room temperature (RT) was 1210 MPa, the elongation only 4%. After low-velocity IF at high and low temperature, the density of the powder alloy was further improved (99.9%), and primary β grains were broken completely, resulting in gaining fine and equiaxed grains. After solution aging heat-treatment, much equiaxed α phases distributed around transformed β matrix evenly, and their size was 1~2 μm. Finally, the powder alloy exhibited tensile strength of 1210 MPa at RT and elongation of 16%, and the strength and plasticity were matched excellently and exceeded technical demands for more.
A technology combining hot isostatic pressing (HIP) with isothermal forging (IF) was used to prepare TC17 powder alloy, and the changes of its microstructure and properties were also researched and analyzed. The results indicated that the powder alloy prepared by HIP of atomized TC17 powder with particle size <104 μm exhibited a homogeneous chemical composition and a fine acicular Widmanst?tten microstructure, and the tensile strength at room temperature (RT) was 1210 MPa, the elongation only 4%. After low-velocity IF at high and low temperature, the density of the powder alloy was further improved (99.9%), and primary β grains were broken completely, resulting in gaining fine and equiaxed grains. After solution aging heat-treatment, much equiaxed α phases distributed around transformed β matrix evenly, and their size was 1~2 μm. Finally, the powder alloy exhibited tensile strength of 1210 MPa at RT and elongation of 16%, and the strength and plasticity were matched excellently and exceeded technical demands for more.
2009, 38(8):1454-1457.
Abstract:
1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid ([BMIM]+[BF4]-) was synthesized using N-methylimidazole and 1-bromobutane as starting materials by two-step method. The obtained ionic liquid was characterized by IR spectra. Gold nanochains were prepared through the reduction of HAuCl4 by NaBH4 in [BMIM]+[BF4]-. UV-Vis spectra and TEM images reveal that the prepared nano gold is mainly chain-like. The ionic liquid not only acts as reaction medium but also as modifier in the preparation of nano gold.
1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid ([BMIM]+[BF4]-) was synthesized using N-methylimidazole and 1-bromobutane as starting materials by two-step method. The obtained ionic liquid was characterized by IR spectra. Gold nanochains were prepared through the reduction of HAuCl4 by NaBH4 in [BMIM]+[BF4]-. UV-Vis spectra and TEM images reveal that the prepared nano gold is mainly chain-like. The ionic liquid not only acts as reaction medium but also as modifier in the preparation of nano gold.
Lei Ming
,
Li Guo
,
Sun Ruiping
,
Pu Minghua
,
Wang Wentao
,
Wu Wei
,
Zhang Xin
,
Zhang Hong
,
Zhang Yong
,
Cheng Cuihua
,
Zhao Yong
2009, 38(8):1458-1461.
Abstract:
A novel chemical solution deposition approach was employed for the preparation of coated-conductor-used RE2O3 (RE=Y, Sm, Eu, Dy, Yb) buffer layers on the biaxial NiW(200) alloy substrate. X-ray diffraction (XRD), scanning electron microscope (SEM), and atomic force microscope (AFM) were used to characterize the phase structure, texture, surface morphology and roughness of the as-received RE2O3 buffer layers. Results show that the obtained RE2O3 buffer layers have well biaxial texture and their surface is smooth and crack free.
A novel chemical solution deposition approach was employed for the preparation of coated-conductor-used RE2O3 (RE=Y, Sm, Eu, Dy, Yb) buffer layers on the biaxial NiW(200) alloy substrate. X-ray diffraction (XRD), scanning electron microscope (SEM), and atomic force microscope (AFM) were used to characterize the phase structure, texture, surface morphology and roughness of the as-received RE2O3 buffer layers. Results show that the obtained RE2O3 buffer layers have well biaxial texture and their surface is smooth and crack free.
2009, 38(8):1462-1466.
Abstract:
The mechanical property and solder ability of SnAgCu system lead-free solder alloys were studied by means of optical microscopy, scanning electron microscopy(SEM), energy dispersive X-ray(EDX) and Instron electrohydraulic servo fatigue tensile tester. The results indicate that proper quantities of Ce can remarkably prolong the creep-rupture life of the Sn3Ag2.8Cu brazing joint at room temperature, and the creep-rupture life of the Sn3Ag2.8Cu-0.1Ce brazing joint is 9 times or more than that of the Sn3Ag2.8Cu; meanwhile, the elongation of the Sn3.0Ag2.8Cu-0.1Ce solder alloy is also obviously improved even up to 15.7%; the intermetallic layers of the Sn3Ag2.8Cu-0.1Ce with copper plate are thicker than that of Sn37Pb, but thinner than that of Sn3Ag2.8Cu.
The mechanical property and solder ability of SnAgCu system lead-free solder alloys were studied by means of optical microscopy, scanning electron microscopy(SEM), energy dispersive X-ray(EDX) and Instron electrohydraulic servo fatigue tensile tester. The results indicate that proper quantities of Ce can remarkably prolong the creep-rupture life of the Sn3Ag2.8Cu brazing joint at room temperature, and the creep-rupture life of the Sn3Ag2.8Cu-0.1Ce brazing joint is 9 times or more than that of the Sn3Ag2.8Cu; meanwhile, the elongation of the Sn3.0Ag2.8Cu-0.1Ce solder alloy is also obviously improved even up to 15.7%; the intermetallic layers of the Sn3Ag2.8Cu-0.1Ce with copper plate are thicker than that of Sn37Pb, but thinner than that of Sn3Ag2.8Cu.
2009, 38(8):1467-1471.
Abstract:
Using different electromagnetic fields application ways, AZ31 magnesium alloy was semi-continuously cast into billets with diameter of 200 mm. The effects of the different electromagnetic fields application ways on the microstructures and mechanical properties of AZ31 billets were investigated. The results show that compared with the conventional direct-chill semi-continuous cast billets, the microstructures in the entire cross section of the AZ31 billets cast in the single alternating magnetic field or the combination of alternating magnetic field and stationary magnetic field are significantly refined, the β-Mg17Al12 phases become fine and dispersive, the difference of the grain size between the border and center of the billet is reduced, and the difference of the microstructures in the billet cast in the combination of alternating magnetic field and stationary magnetic field is smaller than that of the single alternating magnetic field casting. The two electromagnetic field application ways are all beneficial to the homogeneous distributing of the alloy main elements in the cast billets, to great suppressing of macro-segregation and to improving of the mechanical properties of the billets. Compared with the properties of the conventional cast billets, the yield strength and the ultimate tensile strength of the billet cast in the electromagnetic field are increased by 50~60 MPa and 40~50 MPa, respectively, and the elongation is doubled.
Using different electromagnetic fields application ways, AZ31 magnesium alloy was semi-continuously cast into billets with diameter of 200 mm. The effects of the different electromagnetic fields application ways on the microstructures and mechanical properties of AZ31 billets were investigated. The results show that compared with the conventional direct-chill semi-continuous cast billets, the microstructures in the entire cross section of the AZ31 billets cast in the single alternating magnetic field or the combination of alternating magnetic field and stationary magnetic field are significantly refined, the β-Mg17Al12 phases become fine and dispersive, the difference of the grain size between the border and center of the billet is reduced, and the difference of the microstructures in the billet cast in the combination of alternating magnetic field and stationary magnetic field is smaller than that of the single alternating magnetic field casting. The two electromagnetic field application ways are all beneficial to the homogeneous distributing of the alloy main elements in the cast billets, to great suppressing of macro-segregation and to improving of the mechanical properties of the billets. Compared with the properties of the conventional cast billets, the yield strength and the ultimate tensile strength of the billet cast in the electromagnetic field are increased by 50~60 MPa and 40~50 MPa, respectively, and the elongation is doubled.
2009, 38(8):1472-1475.
Abstract:
High-Nb dual phase wrought TiAl alloys were cold-rolled under accurate control by small-pass reduction process. Results show that the deformation of the whole sample is uniform after cold rolling, and the maximum total deformation amount would be more than 20% in the case of no intermediate annealing. The microstructure of the deformed alloy still kept a dual phase structure; γ grains were elongated along rolling direction; the residual lamellar changed from the initial disordered distribution to the distribution of keeping a definite angle to rolling direction. The annealing tests reveal that different reductions, annealing temperatures and annealing time have obvious effect on the mechanical properties and structure of the cold rolled high-Nb TiAl alloy; therefore the intermediate annealing process corresponding to different reductions are also different.
High-Nb dual phase wrought TiAl alloys were cold-rolled under accurate control by small-pass reduction process. Results show that the deformation of the whole sample is uniform after cold rolling, and the maximum total deformation amount would be more than 20% in the case of no intermediate annealing. The microstructure of the deformed alloy still kept a dual phase structure; γ grains were elongated along rolling direction; the residual lamellar changed from the initial disordered distribution to the distribution of keeping a definite angle to rolling direction. The annealing tests reveal that different reductions, annealing temperatures and annealing time have obvious effect on the mechanical properties and structure of the cold rolled high-Nb TiAl alloy; therefore the intermediate annealing process corresponding to different reductions are also different.
2009, 38(8):1476-1479.
Abstract:
CuIn0.7Ga0.3Se2 (CIGS) was synthesized using Cu, In, Ga and Se powders as starting materials by self-propagating high-temperature synthesis method (SHS). The phase and crystallographic structure，chemical composition of the products were characterized by X-ray Diffraction, X-ray Photoelectron Spectroscopy, Energy Dispersive X-ray spectrometer and Laser Raman Spectroscopy. The results show different factors in this process such as reactant ratio, atmosphere pressure etc. obviously influence the stoichiometric composition of the products. An accurate stoichiometric, single-phase chalcopyrite-type CIGS can be prepared by SHS.
CuIn0.7Ga0.3Se2 (CIGS) was synthesized using Cu, In, Ga and Se powders as starting materials by self-propagating high-temperature synthesis method (SHS). The phase and crystallographic structure，chemical composition of the products were characterized by X-ray Diffraction, X-ray Photoelectron Spectroscopy, Energy Dispersive X-ray spectrometer and Laser Raman Spectroscopy. The results show different factors in this process such as reactant ratio, atmosphere pressure etc. obviously influence the stoichiometric composition of the products. An accurate stoichiometric, single-phase chalcopyrite-type CIGS can be prepared by SHS.
2009, 38(8):1480-1483.
Abstract:
The effects of increase extent of voltage on microstructures and corrosion resistance of micro-arc oxidation (MAO) coatings for AZ91D magnesium alloy in silicate electrolyte were investigated. The results showed that with increase of the voltage increase extent, all of the thickness, porosity and bonding force of MAO coating first increased, and then decreased. These parameters were all up to their maximum values when the voltage increase extent was 20 V. However, the roughness of the coatings was always increased with the increasing of voltage increase extent. The coating had the optimum corrosion resistance when voltage increase extent was not below 25V.
The effects of increase extent of voltage on microstructures and corrosion resistance of micro-arc oxidation (MAO) coatings for AZ91D magnesium alloy in silicate electrolyte were investigated. The results showed that with increase of the voltage increase extent, all of the thickness, porosity and bonding force of MAO coating first increased, and then decreased. These parameters were all up to their maximum values when the voltage increase extent was 20 V. However, the roughness of the coatings was always increased with the increasing of voltage increase extent. The coating had the optimum corrosion resistance when voltage increase extent was not below 25V.
2009, 38(8):1484-1486.
Abstract:
A new technique idea of γ-TiAl/Ti alloy composite sheet preparation was presented. Ti-43Al-9V-0.3Y/Ti-6Al-4V composite thin sheet with 3 mm thickness was produced by clad rolling technology at 1150 °C with 80 % total deformation amount. The thickness of Ti-43Al-9V-0.3Y alloy and Ti-6Al-4V alloy is about 2.3 mm and 0.7 mm in the composite sheet, respectively. The composite sheet after clad rolling has intact shape without stress cracking. Analyses show that the interface phases of the composite sheet are mainly composed of α2-Ti3Al. Tensile test reveals that, with increase of Ti-6Al-4V thickness, both the tensile strength and elongation are obviously increased at room temperature. When the thickness of the Ti-6Al-4V layer reaches up to 0.7 mm (the total thickness is 2 mm), the tensile strength and elongation of the composite sheet exceed 800 MPa and 4% at room temperature, respectively. And elongation of the composite sheet exceeds 25% at 700 ℃.
A new technique idea of γ-TiAl/Ti alloy composite sheet preparation was presented. Ti-43Al-9V-0.3Y/Ti-6Al-4V composite thin sheet with 3 mm thickness was produced by clad rolling technology at 1150 °C with 80 % total deformation amount. The thickness of Ti-43Al-9V-0.3Y alloy and Ti-6Al-4V alloy is about 2.3 mm and 0.7 mm in the composite sheet, respectively. The composite sheet after clad rolling has intact shape without stress cracking. Analyses show that the interface phases of the composite sheet are mainly composed of α2-Ti3Al. Tensile test reveals that, with increase of Ti-6Al-4V thickness, both the tensile strength and elongation are obviously increased at room temperature. When the thickness of the Ti-6Al-4V layer reaches up to 0.7 mm (the total thickness is 2 mm), the tensile strength and elongation of the composite sheet exceed 800 MPa and 4% at room temperature, respectively. And elongation of the composite sheet exceeds 25% at 700 ℃.
2009, 38(8):1487-1489.
Abstract:
Using polyvinylidene fluoride membrane (PVDF) as a supported, kerosene as a membrane solvent, 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) as a flowing carrier, the transportation of Pt(IV) in a dispersion supported liquid membrane (DSLM) was investigated. The effects of the volume ratio of the membrane liquid to stripping phase, the concentrations of HCl in the stripping phase, and the acid concentrations in the feed liquid on the transportation of Pt(IV) were studied. The results show that DSLM play an effective role in the transportation of Pt(IV), when the volume ratio of the membrane liquid to the stripping liquid in the dispersion liquid is 140:60, HCl is used as a stripping liquid and its concentrations is 7.0 mol/L, the concentrations of HCl in the feed phase is 0.5 mol/L. Under the optimum condition and upon Pt(IV) initial concentration with 1.0×10-5 mol/L, Pt(IV) can be completely transported within 130 min, but the transportation rate is only 83.6% through traditional SLM.
Using polyvinylidene fluoride membrane (PVDF) as a supported, kerosene as a membrane solvent, 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) as a flowing carrier, the transportation of Pt(IV) in a dispersion supported liquid membrane (DSLM) was investigated. The effects of the volume ratio of the membrane liquid to stripping phase, the concentrations of HCl in the stripping phase, and the acid concentrations in the feed liquid on the transportation of Pt(IV) were studied. The results show that DSLM play an effective role in the transportation of Pt(IV), when the volume ratio of the membrane liquid to the stripping liquid in the dispersion liquid is 140:60, HCl is used as a stripping liquid and its concentrations is 7.0 mol/L, the concentrations of HCl in the feed phase is 0.5 mol/L. Under the optimum condition and upon Pt(IV) initial concentration with 1.0×10-5 mol/L, Pt(IV) can be completely transported within 130 min, but the transportation rate is only 83.6% through traditional SLM.
2009, 38(8):1490-1494.
Abstract:
The microstructures and tensile properties of Ti-1300 alloy after solid-solution treatment at different temperatures followed by slow heating aging were studied. The results indicate that the different phase transformations of the alloy took place after the solid-solution/aging treatment at up-and-down phase transformation temperature (PTT), and the corresponding tensile properties of the alloy also showed obvious difference. β→ω transformation occurred when the samples were solid-solution treated at the upper PTT and then aged heating slowly to 500 ℃. After this treatment, the alloy had high strength but low plasticity. On the contrary, when the samples were solid-solution treated at the down PTT followed by furnace heating ageing, β→α transformation occurred and the tensile strength of the alloy was 1430 MPa and elongation was 8.0% after aging heating up to 570 ℃.
The microstructures and tensile properties of Ti-1300 alloy after solid-solution treatment at different temperatures followed by slow heating aging were studied. The results indicate that the different phase transformations of the alloy took place after the solid-solution/aging treatment at up-and-down phase transformation temperature (PTT), and the corresponding tensile properties of the alloy also showed obvious difference. β→ω transformation occurred when the samples were solid-solution treated at the upper PTT and then aged heating slowly to 500 ℃. After this treatment, the alloy had high strength but low plasticity. On the contrary, when the samples were solid-solution treated at the down PTT followed by furnace heating ageing, β→α transformation occurred and the tensile strength of the alloy was 1430 MPa and elongation was 8.0% after aging heating up to 570 ℃.
2009, 38(8):1495-1500.
Abstract:
Research and development of semisolid metal slurry processing technology was outlined; and a few representative SSM (semisolid metal processing) methods and the corresponding slurry processing technologies were presented; moreover, the formation mechanism of non-dendritic microstructure under coerced convection condition was summarized. The rheoforming route, whose process flow was simple and prime cost was low, has become the development direction at present. The necessary condition of manufacturing high-quality semisolid processed parts is that the supplied semisolid slurry has high density of nuclei suspending uniformly in the bulk melt.
Research and development of semisolid metal slurry processing technology was outlined; and a few representative SSM (semisolid metal processing) methods and the corresponding slurry processing technologies were presented; moreover, the formation mechanism of non-dendritic microstructure under coerced convection condition was summarized. The rheoforming route, whose process flow was simple and prime cost was low, has become the development direction at present. The necessary condition of manufacturing high-quality semisolid processed parts is that the supplied semisolid slurry has high density of nuclei suspending uniformly in the bulk melt.
2009, 38(8):1501-1504.
Abstract:
Owing to the exhaustion of non-renewable resources such as fossil fuels and the increasing seriousness of environmental pollution, it is urgent to find alternative energy. Hydrogen energy has been extensively studied for its cleanness and sustainability. An important issue for the utilization of hydrogen energy is the hydrogen storage and transportation. The complex hydrogen storage materials with Al–H bond have been regarded as promising materials for hydrogen storage due to its large hydrogen storage capacity. This paper mainly introduced the new research progress of the composition, preparation, crystal structure and hydrogen storage properties of several kinds of complex hydrogen storage materials with Al–H bond, such as alkali metal, alkaline-earth metal and some other metal-aluminum hydrides.
Owing to the exhaustion of non-renewable resources such as fossil fuels and the increasing seriousness of environmental pollution, it is urgent to find alternative energy. Hydrogen energy has been extensively studied for its cleanness and sustainability. An important issue for the utilization of hydrogen energy is the hydrogen storage and transportation. The complex hydrogen storage materials with Al–H bond have been regarded as promising materials for hydrogen storage due to its large hydrogen storage capacity. This paper mainly introduced the new research progress of the composition, preparation, crystal structure and hydrogen storage properties of several kinds of complex hydrogen storage materials with Al–H bond, such as alkali metal, alkaline-earth metal and some other metal-aluminum hydrides.
