Volume 39,Issue 1,2010 Table of Contents
2010, 39(1):1-5.
Abstract:
Hydrogenation of Ti-6Al-4V titanium alloys was carried out in a special furnace through the accumulated flux method, and OM, XRD and TEM techniques were used to investigate the microstructure evolution of the hydrogenated Ti-6Al-4V titanium alloy. The hydrogenation of the Ti-6Al-4V titanium alloy with the hydrogen content of 0.30 wt% makes the α phase fraction decrease compared with that of the as-received Ti-6Al-4V titanium alloy, but it makes the β phase fraction increase. The δ hydride (TiH2 phase) occurs in the hydrogenated Ti-6Al-4V titanium alloy when the hydrogen content is more than 0.3 wt%. The shear deformation is main pattern in the transformation processes from β-Ti(H) phase to α-Ti phase and δ hydride (TiH2 phase). The phase transformation temperature of the hydrogenated Ti-6Al-4V titanium alloy decreases by 180 °C compared with that of the as-received Ti-6Al-4V titanium alloy, and it is related to the phase fraction and phase transformation.
Hydrogenation of Ti-6Al-4V titanium alloys was carried out in a special furnace through the accumulated flux method, and OM, XRD and TEM techniques were used to investigate the microstructure evolution of the hydrogenated Ti-6Al-4V titanium alloy. The hydrogenation of the Ti-6Al-4V titanium alloy with the hydrogen content of 0.30 wt% makes the α phase fraction decrease compared with that of the as-received Ti-6Al-4V titanium alloy, but it makes the β phase fraction increase. The δ hydride (TiH2 phase) occurs in the hydrogenated Ti-6Al-4V titanium alloy when the hydrogen content is more than 0.3 wt%. The shear deformation is main pattern in the transformation processes from β-Ti(H) phase to α-Ti phase and δ hydride (TiH2 phase). The phase transformation temperature of the hydrogenated Ti-6Al-4V titanium alloy decreases by 180 °C compared with that of the as-received Ti-6Al-4V titanium alloy, and it is related to the phase fraction and phase transformation.
2010, 39(1):6-9.
Abstract:
Mo-Cu (Mo:Cu=60:40, mass ratio) predecessor powder was prepared by chemical co-precipitation taking (NH4)6Mo7O24·2H2O and CuSO4·5H2O as starting materials. And then the Mo-Cu predecessor powder was reduced by hydrogen in closed circulation system to prepare the Mo-Cu composite nano-powder. The results reveal that conditions of the chemical co-precipitation are that reaction temperature is (50±5) °C, pH value (5.1±0.1), and ageing time (9±1) h. Under the conditions mentioned above, the average particle size of the prepared the Mo-Cu predecessor powder is 20 nm. The hydrogen reduction temperature during closed circulation is 650 °C. The particle size of obtained Mo-Cu composite powder is less than 100 nm.
Mo-Cu (Mo:Cu=60:40, mass ratio) predecessor powder was prepared by chemical co-precipitation taking (NH4)6Mo7O24·2H2O and CuSO4·5H2O as starting materials. And then the Mo-Cu predecessor powder was reduced by hydrogen in closed circulation system to prepare the Mo-Cu composite nano-powder. The results reveal that conditions of the chemical co-precipitation are that reaction temperature is (50±5) °C, pH value (5.1±0.1), and ageing time (9±1) h. Under the conditions mentioned above, the average particle size of the prepared the Mo-Cu predecessor powder is 20 nm. The hydrogen reduction temperature during closed circulation is 650 °C. The particle size of obtained Mo-Cu composite powder is less than 100 nm.
2010, 39(1):10-16.
Abstract:
The influence of nano-Al2O3 particles on nickel deposition on copper matrix from acid sulphate solution was studied under various potentials (vs. SCE) by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The results show that the beginning potential of Ni-Al2O3 co-deposition is at –740 mV or so. The effect of nano-Al2O3 particles on nickel deposition process may be different under various potentials. In the potentials range from –740 to –830 mV, Al2O3 particles on cathode surface may be favorable for nickel deposition nucleation and promote electron crystallization nucleation because the induction period tm corresponding to the peak current of Ni-Al2O3 co-deposition is apparently shortened, compared with that of pure Ni deposition. However, Al2O3 particles adsorbed on cathode surface may obstruct electric discharge of partial ions and mass transmission process, resulting in the impedance increment of Ni-Al2O3 co-deposition, especially in the potentials range from –250 to –650 mV. The favorable effect of Al2O3 particles weaken in the range of high over potential, and the particles accumulated on electrode surface will decrease the reduction current of Ni-Al2O3 deposition. At the potential –890 mV, the nucleation process of Ni-Al2O3 co-deposition at initial stage follows the instantaneous model of Scharifker-Hill with three-dimensional fashion.
The influence of nano-Al2O3 particles on nickel deposition on copper matrix from acid sulphate solution was studied under various potentials (vs. SCE) by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The results show that the beginning potential of Ni-Al2O3 co-deposition is at –740 mV or so. The effect of nano-Al2O3 particles on nickel deposition process may be different under various potentials. In the potentials range from –740 to –830 mV, Al2O3 particles on cathode surface may be favorable for nickel deposition nucleation and promote electron crystallization nucleation because the induction period tm corresponding to the peak current of Ni-Al2O3 co-deposition is apparently shortened, compared with that of pure Ni deposition. However, Al2O3 particles adsorbed on cathode surface may obstruct electric discharge of partial ions and mass transmission process, resulting in the impedance increment of Ni-Al2O3 co-deposition, especially in the potentials range from –250 to –650 mV. The favorable effect of Al2O3 particles weaken in the range of high over potential, and the particles accumulated on electrode surface will decrease the reduction current of Ni-Al2O3 deposition. At the potential –890 mV, the nucleation process of Ni-Al2O3 co-deposition at initial stage follows the instantaneous model of Scharifker-Hill with three-dimensional fashion.
2010, 39(1):17-21.
Abstract:
In order to fabricate highly dense W/Cu20 (mass fraction, similarly hereinafter) composite materials, two kinds of tungsten powder with different particle size, A and B, were used. The W powder with different ratios of A and B were directly mixed with copper powder and W/Cu20 mixed powder was obtained. Almost fully dense W-Cu composite materials were fabricated by solid-state hot pressing. The observation of microstructure shows that with increasing of the fine W powder (B) content, the pores formed by the coarse W powder (A) decrease and the pores by the fine W powder increase gradually. Rather dense microstructure is obtained when the W particle distribution is 80%A+20%B. The W/Cu20 with 98.6% relative density is obtained under the processing conditions of sintering temperature of 1060 °C, pressure of 85 MPa and holding time of 3 h. Copper forms into a network structure around the coarse W particles and the fine W particles.
In order to fabricate highly dense W/Cu20 (mass fraction, similarly hereinafter) composite materials, two kinds of tungsten powder with different particle size, A and B, were used. The W powder with different ratios of A and B were directly mixed with copper powder and W/Cu20 mixed powder was obtained. Almost fully dense W-Cu composite materials were fabricated by solid-state hot pressing. The observation of microstructure shows that with increasing of the fine W powder (B) content, the pores formed by the coarse W powder (A) decrease and the pores by the fine W powder increase gradually. Rather dense microstructure is obtained when the W particle distribution is 80%A+20%B. The W/Cu20 with 98.6% relative density is obtained under the processing conditions of sintering temperature of 1060 °C, pressure of 85 MPa and holding time of 3 h. Copper forms into a network structure around the coarse W particles and the fine W particles.
2010, 39(1):22-26.
Abstract:
The changes of the microstructure and the microhardness at the weld interface of near isothermally forged Ti3Al/TC11 dual alloys before and after gradient heat treatment were investigated. The results indicate that the stability of α2 phase and distribution in the grain boundary results in slight changes of microstructures at heat-affected zone on Ti3Al side, but the changes of the microstructure in the weld zone are relatively obvious due to the diffusions of elements such as Ti, Al, Nb and so on. Because growing-up of the α and α2 phase is restricted each other, the continual α or α2 phase grain boundary can not be formed. After gradient heat treatment, the matrix microstructure of the TC11 alloy changes from basketweave structure to equiaxed structure. Because of the diffusions of Ti, Al and Nb, the sizes of α and α2 phases become small and their distribution become dispersive, resulting in the increase in microhardness.
The changes of the microstructure and the microhardness at the weld interface of near isothermally forged Ti3Al/TC11 dual alloys before and after gradient heat treatment were investigated. The results indicate that the stability of α2 phase and distribution in the grain boundary results in slight changes of microstructures at heat-affected zone on Ti3Al side, but the changes of the microstructure in the weld zone are relatively obvious due to the diffusions of elements such as Ti, Al, Nb and so on. Because growing-up of the α and α2 phase is restricted each other, the continual α or α2 phase grain boundary can not be formed. After gradient heat treatment, the matrix microstructure of the TC11 alloy changes from basketweave structure to equiaxed structure. Because of the diffusions of Ti, Al and Nb, the sizes of α and α2 phases become small and their distribution become dispersive, resulting in the increase in microhardness.
2010, 39(1):27-31.
Abstract:
Effect of Mn substitution for Ni on phase constitution and electrochemical characteristics of La2Mg0.9Al0.1Ni7.5-xCo1.5Mnx (x=0, 0.3, 0.6, 0.9) hydrogen storage alloys was studied. It is found that Mn substitution will change phase composition and phase constitution of the alloys. LaNi3 phase disappears; the components of αLa2Ni7 first increases with Mn content from x=0 to x=0.3 and then decreases from x=0.6 to 0.9. Both component of LaMgNi4 phase and La5Ni19 phase increase as x increases in the alloys. Replacement of Ni by Mn will lower hydrogen storage capacity, maximum electrochemical discharge capacity and activation property of the alloy electrodes. La2Mg0.9Al0.1Ni7.2Co1.5Mn0.3 hydride electrode shows the best cycle stability. The high rate dischargeability of the alloys decreases with the increase of Mn content, which would be attributed to the decrease of exchange current density (I0) and diffusion coefficient of the hydrogen atom (D).
Effect of Mn substitution for Ni on phase constitution and electrochemical characteristics of La2Mg0.9Al0.1Ni7.5-xCo1.5Mnx (x=0, 0.3, 0.6, 0.9) hydrogen storage alloys was studied. It is found that Mn substitution will change phase composition and phase constitution of the alloys. LaNi3 phase disappears; the components of αLa2Ni7 first increases with Mn content from x=0 to x=0.3 and then decreases from x=0.6 to 0.9. Both component of LaMgNi4 phase and La5Ni19 phase increase as x increases in the alloys. Replacement of Ni by Mn will lower hydrogen storage capacity, maximum electrochemical discharge capacity and activation property of the alloy electrodes. La2Mg0.9Al0.1Ni7.2Co1.5Mn0.3 hydride electrode shows the best cycle stability. The high rate dischargeability of the alloys decreases with the increase of Mn content, which would be attributed to the decrease of exchange current density (I0) and diffusion coefficient of the hydrogen atom (D).
2010, 39(1):32-36.
Abstract:
The laser welding-brazing experiment of Ti/Al dissimilar alloys was performed with rectangular spot CO2 laser as heat resource and AlSi12 as the filler wire. It is found that the porosity in the seam is a main factor for weak joint. The results indicate that the gasification of element Mg causes the formation of porosity during the welding. The offset of the laser beam toward Ti alloy and heat input markedly influence the formation of the porosity. In general no porosity is observed in the seam when the length of claviform intermetallic compound is less than 10 μm. Moreover, the microstructure in the seam plays a key role in the diameter of the pore.
The laser welding-brazing experiment of Ti/Al dissimilar alloys was performed with rectangular spot CO2 laser as heat resource and AlSi12 as the filler wire. It is found that the porosity in the seam is a main factor for weak joint. The results indicate that the gasification of element Mg causes the formation of porosity during the welding. The offset of the laser beam toward Ti alloy and heat input markedly influence the formation of the porosity. In general no porosity is observed in the seam when the length of claviform intermetallic compound is less than 10 μm. Moreover, the microstructure in the seam plays a key role in the diameter of the pore.
8 Characterization of Self-Assembly Monolayers in High-Magnetic Gravity Field and Response Mechanism
2010, 39(1):37-41.
Abstract:
Functional-group-modified surface of titanium alloys was derived by self-assembly method in the high-magnetic gravity field simulated by superconductive magnet. Contact angle and surface energy of the surface were measured and calculated by a contact angle meter, and surface roughness of the polished and eroded samples was analyzed by atomic force microscopy (AFM). The contact angle test results show that the developing tendency of contact angle and surface energy of the six test surfaces for the three fluids is basically consistent. The contact angle of the surface chemically modified by -PO4H2 functional group is decreased, and its surface energy is higher in the magnet than that out of the magnet due to the high magnetic effect. The acceleration of gravity is inversely proportional to the contact angle, and proportional to the surface energy when magnetic field intensity are equal.
Functional-group-modified surface of titanium alloys was derived by self-assembly method in the high-magnetic gravity field simulated by superconductive magnet. Contact angle and surface energy of the surface were measured and calculated by a contact angle meter, and surface roughness of the polished and eroded samples was analyzed by atomic force microscopy (AFM). The contact angle test results show that the developing tendency of contact angle and surface energy of the six test surfaces for the three fluids is basically consistent. The contact angle of the surface chemically modified by -PO4H2 functional group is decreased, and its surface energy is higher in the magnet than that out of the magnet due to the high magnetic effect. The acceleration of gravity is inversely proportional to the contact angle, and proportional to the surface energy when magnetic field intensity are equal.
2010, 39(1):42-45.
Abstract:
Surface self-nanocrystallization (SSNC) by means of high energy shot peening(HESP) was applied to produce nanostructures on the bonding surface of TA17 titanium alloy and 0Cr18Ni9Ti stainless steel bars and nanocrystalline structure layers with certain thickness were formed on the bonding surface of samples. TA17 and 0Cr18Ni9Ti bars were bonded by constant temperature and pressure diffusion bonding (CTPDB) and impact pressure diffusion bonding (IPDB) respectively on Gleeble-1500D tester. Tensile strength was tested, and the joint fractures and microstructures were analyzed. The results show that thinner intermetallic compound layer is formed on the interface of joints by IPDB which has a tensile strength of 384.0 MPa. Fracture of IPDB joints present brittle characteristic.
Surface self-nanocrystallization (SSNC) by means of high energy shot peening(HESP) was applied to produce nanostructures on the bonding surface of TA17 titanium alloy and 0Cr18Ni9Ti stainless steel bars and nanocrystalline structure layers with certain thickness were formed on the bonding surface of samples. TA17 and 0Cr18Ni9Ti bars were bonded by constant temperature and pressure diffusion bonding (CTPDB) and impact pressure diffusion bonding (IPDB) respectively on Gleeble-1500D tester. Tensile strength was tested, and the joint fractures and microstructures were analyzed. The results show that thinner intermetallic compound layer is formed on the interface of joints by IPDB which has a tensile strength of 384.0 MPa. Fracture of IPDB joints present brittle characteristic.
2010, 39(1):46-49.
Abstract:
Al-Ti-C master alloys were prepared by laser-induced self-propagating high-temperature synthesis (SHS). The influence of different irradiation parameters of the laser on the microstructure of synthesized product was investigated, and the refinement effect of the obtained master alloy for commercially pure aluminium is also evaluated. The results show that the laser irradiation parameters have significant influence on the microstructure of the Al-Ti-C master alloys. Under the condition of the laser irradiation time 1.0 s and the power in 1000 W, the microstructures of prepared Al-Ti-C master alloys are composed of the granular TiAl3 and TiC, which are dispersive. The diameter of TiC is about 1 μm, and that of the granular TiAl3 is about 1.5 μm. The 0.1% addition of this master alloy to the molten commercially pure aluminium is most excellent; the average grain size is 120 μm after refinement.
Al-Ti-C master alloys were prepared by laser-induced self-propagating high-temperature synthesis (SHS). The influence of different irradiation parameters of the laser on the microstructure of synthesized product was investigated, and the refinement effect of the obtained master alloy for commercially pure aluminium is also evaluated. The results show that the laser irradiation parameters have significant influence on the microstructure of the Al-Ti-C master alloys. Under the condition of the laser irradiation time 1.0 s and the power in 1000 W, the microstructures of prepared Al-Ti-C master alloys are composed of the granular TiAl3 and TiC, which are dispersive. The diameter of TiC is about 1 μm, and that of the granular TiAl3 is about 1.5 μm. The 0.1% addition of this master alloy to the molten commercially pure aluminium is most excellent; the average grain size is 120 μm after refinement.
2010, 39(1):50-54.
Abstract:
Effect of TiF3 addition as the catalyst on the hydrogen desorption property of Mg95Ni5 composites by hydriding combustion synthesis (HCS) was investigated. Addition of 1% TiF3 (molar fraction) can get the best hydrogen desorption property for Mg95Ni5 mechanically milled for 10 h, which could desorb 5.20% (mass fraction) of H2 in 1800 s at 523 K. The apparent activation energy of hydrogen desorption for Mg95Ni5+1%TiF3 milled for 10 h was decreased to 86 kJ/mol from 124 kJ/mol of Mg95Ni5. Results show that catalytic effect of TiF3 could be attributed to the formation of MgF2 and Tix+ hydrides which destabilize the bonding of Mg-H.
Effect of TiF3 addition as the catalyst on the hydrogen desorption property of Mg95Ni5 composites by hydriding combustion synthesis (HCS) was investigated. Addition of 1% TiF3 (molar fraction) can get the best hydrogen desorption property for Mg95Ni5 mechanically milled for 10 h, which could desorb 5.20% (mass fraction) of H2 in 1800 s at 523 K. The apparent activation energy of hydrogen desorption for Mg95Ni5+1%TiF3 milled for 10 h was decreased to 86 kJ/mol from 124 kJ/mol of Mg95Ni5. Results show that catalytic effect of TiF3 could be attributed to the formation of MgF2 and Tix+ hydrides which destabilize the bonding of Mg-H.
2010, 39(1):55-59.
Abstract:
High alloying GH742 alloys exhibit severe dendritic segregation with Nb and Ti intensively segregated to the interdendritic regions, leading to the precipitation of MC carbide, (γ+γ′) eutectic, Laves phase and δ phase. High content of Mo as well as its dendritic segregation is the significant reason for the precipitation of σ phase. Two phases containing rare earth elements, Ni5Ce phase and RE-O-S phase, are precipitated in the interdendritic regions due to the enrichment of La and Ce. Different from other superalloys, both eutectic reactions of (γ+γ′) and (γ+Laves) take place in sequence during the solidification process of GH742 alloys owing to the high contents of Al, Ti and Nb. The solidification temperature range of GH742 alloys is between 1346 and 1190 oC, and the solidification sequence is γ, MC, (γ+γ′), Laves and Ni5Ce, which is determined by differential thermal analysis and solidification microstructure characterization.
High alloying GH742 alloys exhibit severe dendritic segregation with Nb and Ti intensively segregated to the interdendritic regions, leading to the precipitation of MC carbide, (γ+γ′) eutectic, Laves phase and δ phase. High content of Mo as well as its dendritic segregation is the significant reason for the precipitation of σ phase. Two phases containing rare earth elements, Ni5Ce phase and RE-O-S phase, are precipitated in the interdendritic regions due to the enrichment of La and Ce. Different from other superalloys, both eutectic reactions of (γ+γ′) and (γ+Laves) take place in sequence during the solidification process of GH742 alloys owing to the high contents of Al, Ti and Nb. The solidification temperature range of GH742 alloys is between 1346 and 1190 oC, and the solidification sequence is γ, MC, (γ+γ′), Laves and Ni5Ce, which is determined by differential thermal analysis and solidification microstructure characterization.
2010, 39(1):60-64.
Abstract:
Ni-W-P layers were formed on a low-carbon steel substrate by direct-current electroplating method. The effects of current density, pH value and bath temperature on the composition, surface morphology, and microstructure of Ni-W-P layers were studied by X-ray fluorescence (XRF), scanning electron microscope (SEM), auger electron spectroscopy (AES) and X-ray diffraction (XRD). The results indicate that the change of current density and pH value influenced the composition of Ni-W-P layer greatly, but the change of current density, pH value and bath temperature hardly influenced the thickness of Ni-W-P layer. As current density and bath temperature increased, current efficiency decreased and increased, respectively, and current efficiency reached the maximum value when pH value is 7.0. The structure of Ni-W-P layer was greatly influenced by pH value, and a well-preferred orientation along Ni (111) direction was shown when pH value was 8.0. Synchronously, the microhardness of Ni-W-P layer reached the maximum value of 7130 MPa. At last, electroplating mechanism of Ni-W-P layer was discussed further.
Ni-W-P layers were formed on a low-carbon steel substrate by direct-current electroplating method. The effects of current density, pH value and bath temperature on the composition, surface morphology, and microstructure of Ni-W-P layers were studied by X-ray fluorescence (XRF), scanning electron microscope (SEM), auger electron spectroscopy (AES) and X-ray diffraction (XRD). The results indicate that the change of current density and pH value influenced the composition of Ni-W-P layer greatly, but the change of current density, pH value and bath temperature hardly influenced the thickness of Ni-W-P layer. As current density and bath temperature increased, current efficiency decreased and increased, respectively, and current efficiency reached the maximum value when pH value is 7.0. The structure of Ni-W-P layer was greatly influenced by pH value, and a well-preferred orientation along Ni (111) direction was shown when pH value was 8.0. Synchronously, the microhardness of Ni-W-P layer reached the maximum value of 7130 MPa. At last, electroplating mechanism of Ni-W-P layer was discussed further.
2010, 39(1):65-68.
Abstract:
Dense and uniform Sip/LG5 composites were fabricated by squeeze casting process, and then were treated by high temperature diffusion. Microstructure observation indicated that Si transformed from irregular sharp-particles to 3D network structure after high temperature diffusion treatment. Si-Al interface of 3D-Sip/LG5 composites is smoother and has better bonding degree, compared with the interface of the untreated composites. There are Si precipitation in the interface and the matrix of 3D-Sip/LG5 composites. Twin crystals were observed in the matrix of 3D-Sip/LG5 composites. The average linear thermal expansion (CTE) of the composites is decreased by 10.5% after high temperature diffusion treatment. However, the thermal conductivity of 3D-Sip/LG5 composites does not change significantly due to the decreased Si precipitation in the interface and matrix by 3D network structure of Si.
Dense and uniform Sip/LG5 composites were fabricated by squeeze casting process, and then were treated by high temperature diffusion. Microstructure observation indicated that Si transformed from irregular sharp-particles to 3D network structure after high temperature diffusion treatment. Si-Al interface of 3D-Sip/LG5 composites is smoother and has better bonding degree, compared with the interface of the untreated composites. There are Si precipitation in the interface and the matrix of 3D-Sip/LG5 composites. Twin crystals were observed in the matrix of 3D-Sip/LG5 composites. The average linear thermal expansion (CTE) of the composites is decreased by 10.5% after high temperature diffusion treatment. However, the thermal conductivity of 3D-Sip/LG5 composites does not change significantly due to the decreased Si precipitation in the interface and matrix by 3D network structure of Si.
2010, 39(1):69-71.
Abstract:
Influence of high-temperature aging time on microstructure and stress rupture property of DZ951 superalloys was investigated by optical microscopy (OM) and scanning electronic microscopy (SEM). The results reveal that carbide changes from skeleton-like of as-cast alloy to block-like and discontinuously distributes in grain boundary when the alloy is aged at 1130 °C. g￠ cubicity decreases and the size of g￠ phase increases with the elongation of holding time at 1130 °C. g￠ coarsens and rafts when the holding time is 6 h. For solid solution of some g￠, fine and spherical g￠ phase precipitates during the following cooling process after 1130 °C aging treatment. The volume fraction of fine g￠ phase increases with prolonging the holding time. The stress rupture life of DZ951 alloy at 1100 °C/60 MPa reduces and the elongation increases with the prolongation of holding time. Coarsening and rafting of g￠ is deleterious to the stress rupture life for alloys.
Influence of high-temperature aging time on microstructure and stress rupture property of DZ951 superalloys was investigated by optical microscopy (OM) and scanning electronic microscopy (SEM). The results reveal that carbide changes from skeleton-like of as-cast alloy to block-like and discontinuously distributes in grain boundary when the alloy is aged at 1130 °C. g￠ cubicity decreases and the size of g￠ phase increases with the elongation of holding time at 1130 °C. g￠ coarsens and rafts when the holding time is 6 h. For solid solution of some g￠, fine and spherical g￠ phase precipitates during the following cooling process after 1130 °C aging treatment. The volume fraction of fine g￠ phase increases with prolonging the holding time. The stress rupture life of DZ951 alloy at 1100 °C/60 MPa reduces and the elongation increases with the prolongation of holding time. Coarsening and rafting of g￠ is deleterious to the stress rupture life for alloys.
2010, 39(1):72-75.
Abstract:
HFIS304 self-lubricating coating was prepared by high-energy ball milling, cold isostatic pressing and high-frequency induction sintering (HFIS) on a Ni-based superalloy rod, and its composition was NiCr (80/20) matrix (60wt%) combined with Cr2O3 (20wt%), Ag (10wt%) and eutectic BaF2/CaF2 (10wt%) as solid self-lubricating additives. The microstructure of HFIS304 coating was dense, and three kinds of lubricating phases were fine. Research shows that wear resistance and friction coefficient of the HFIS304 coating are superior to that of the PS304 coating in the range from room temperature to 600 °C.
HFIS304 self-lubricating coating was prepared by high-energy ball milling, cold isostatic pressing and high-frequency induction sintering (HFIS) on a Ni-based superalloy rod, and its composition was NiCr (80/20) matrix (60wt%) combined with Cr2O3 (20wt%), Ag (10wt%) and eutectic BaF2/CaF2 (10wt%) as solid self-lubricating additives. The microstructure of HFIS304 coating was dense, and three kinds of lubricating phases were fine. Research shows that wear resistance and friction coefficient of the HFIS304 coating are superior to that of the PS304 coating in the range from room temperature to 600 °C.
2010, 39(1):76-79.
Abstract:
La0.3Sr0.7FeO3 (LSFO) thin films were prepared by RF magnetron sputtering method. The resistance-temperature relation shows that the film favors the semiconductive conduction in the testing temperature range, which arises from the charge ordering of Fe3+ and Fe5+ ions. The charge ordering transition happened at T=250 K. The laser irradiation induces a decrease of the resistance of the film and the maximum relative change in the photoinduced resistance is about 56.3% at T=190 K. The analysis of the resistance-temperature relation using the variable range hoping (VRH) model shows that the intrinsic mechanism of the laser irradiation is the delocalization of the electrons.
La0.3Sr0.7FeO3 (LSFO) thin films were prepared by RF magnetron sputtering method. The resistance-temperature relation shows that the film favors the semiconductive conduction in the testing temperature range, which arises from the charge ordering of Fe3+ and Fe5+ ions. The charge ordering transition happened at T=250 K. The laser irradiation induces a decrease of the resistance of the film and the maximum relative change in the photoinduced resistance is about 56.3% at T=190 K. The analysis of the resistance-temperature relation using the variable range hoping (VRH) model shows that the intrinsic mechanism of the laser irradiation is the delocalization of the electrons.
2010, 39(1):80-84.
Abstract:
The rare earth element yttrium was added into 7055 aluminum alloys in the form of Al-Y intermediate alloy. The thermodynamic mechanism during melting and effect mechanism during solidification of yttrium were analyzed based on the classical theories of physical chemistry and crystal growth. Results show that there are strong binding between yttrium and impurity elements, such as oxygen, hydrogen, nitrogen, sulfur, iron and so on, which can purify the aluminum melt. The grain size of as-cast alloys is decreased from 60-70 μm to 40-50 μm after yttrium addition. It is due to the small solubility of yttrium element in molten aluminum. Most of yttrium segregates at the solid-liquid boundary, and prevent the Zn, Mg and Cu atoms from diffusing resulting in the constitutional supercooling at the frontier of solidification, which accelerate the growth of cellular dendrite. Furthermore, the amount of eutectic increases, the size of which is smaller than that without yttrium.
The rare earth element yttrium was added into 7055 aluminum alloys in the form of Al-Y intermediate alloy. The thermodynamic mechanism during melting and effect mechanism during solidification of yttrium were analyzed based on the classical theories of physical chemistry and crystal growth. Results show that there are strong binding between yttrium and impurity elements, such as oxygen, hydrogen, nitrogen, sulfur, iron and so on, which can purify the aluminum melt. The grain size of as-cast alloys is decreased from 60-70 μm to 40-50 μm after yttrium addition. It is due to the small solubility of yttrium element in molten aluminum. Most of yttrium segregates at the solid-liquid boundary, and prevent the Zn, Mg and Cu atoms from diffusing resulting in the constitutional supercooling at the frontier of solidification, which accelerate the growth of cellular dendrite. Furthermore, the amount of eutectic increases, the size of which is smaller than that without yttrium.
2010, 39(1):85-89.
Abstract:
spicule and flake with big sizes on the surface of the milling-free powders, while on the surface of milled powders ZnO was shaped mainly as spicule with small sizes. Nodules of virtually pure silver atoms formed on the surface of powder during internal oxidation, which is attributed to the compressive stress caused by the expansion of ZnO in the silver-matrix during internal oxidation.
spicule and flake with big sizes on the surface of the milling-free powders, while on the surface of milled powders ZnO was shaped mainly as spicule with small sizes. Nodules of virtually pure silver atoms formed on the surface of powder during internal oxidation, which is attributed to the compressive stress caused by the expansion of ZnO in the silver-matrix during internal oxidation.
2010, 39(1):90-95.
Abstract:
Through substitution of mixed rare earth elements Ce, Pr and Nd for La, (La0.7Ce0.1PrxNd2-x)0.67Mg0.33Ni3.0 (x=0, 0.1, 0.2) hydrogen storage alloys were prepared by induction melting followed by annealing treatment. Influences of partial substitution of rare earth elements Ce, Nd and Pr for La on phase structure and electrochemical properties of (La0.7Ce0.1PrxNd2-x)0.67Mg0.33Ni3.0 (x=0, 0.1, 0.2 ) were investigated by means of X-ray diffraction (XRD), electron probe X-ray microanalysis (EPMA) and electrochemical measurements. XRD and back scattered electron images analysis shows that all of the alloys were composed of main phase with PuNi3-type structure and small amount of second phase of LaMgNi4. With the addition of the mixed rare earth elements and increasing of Pr content x, the lattice parameters c and c/a of the PuNi3-type structure increase while cell volume and a decrease. Compared with La0.67Mg0.33Ni3.0, the electrochemical properties of the (La0.7Ce0.1PrxNd0.2-x)0.67Mg0.33Ni3.0 alloys were improved obviously. Although the electrochemical capacities of the alloys decreased little compared with that of La0.67Mg0.33Ni3.0 (392.0 mAh/g), the electrode capacities became increasing (384 mAh/g) when Pr content x increased. After 100 cycles, the capacity retention rates of the electrodes increased from 64% to 82.6%-83% and the high-rate dischargeabilities (HRDs) of the alloys increased from 78.4% to 89.4%-91.1%.
Through substitution of mixed rare earth elements Ce, Pr and Nd for La, (La0.7Ce0.1PrxNd2-x)0.67Mg0.33Ni3.0 (x=0, 0.1, 0.2) hydrogen storage alloys were prepared by induction melting followed by annealing treatment. Influences of partial substitution of rare earth elements Ce, Nd and Pr for La on phase structure and electrochemical properties of (La0.7Ce0.1PrxNd2-x)0.67Mg0.33Ni3.0 (x=0, 0.1, 0.2 ) were investigated by means of X-ray diffraction (XRD), electron probe X-ray microanalysis (EPMA) and electrochemical measurements. XRD and back scattered electron images analysis shows that all of the alloys were composed of main phase with PuNi3-type structure and small amount of second phase of LaMgNi4. With the addition of the mixed rare earth elements and increasing of Pr content x, the lattice parameters c and c/a of the PuNi3-type structure increase while cell volume and a decrease. Compared with La0.67Mg0.33Ni3.0, the electrochemical properties of the (La0.7Ce0.1PrxNd0.2-x)0.67Mg0.33Ni3.0 alloys were improved obviously. Although the electrochemical capacities of the alloys decreased little compared with that of La0.67Mg0.33Ni3.0 (392.0 mAh/g), the electrode capacities became increasing (384 mAh/g) when Pr content x increased. After 100 cycles, the capacity retention rates of the electrodes increased from 64% to 82.6%-83% and the high-rate dischargeabilities (HRDs) of the alloys increased from 78.4% to 89.4%-91.1%.
2010, 39(1):96-100.
Abstract:
Microstructures and mechanical properties of Mg-6Al-1.2Y-0.9Nd magnesium alloy with Sm addition were investigated through OM, SEM, EDS and XRD. The results show that Sm combines firstly with Al to form dispersed, high-melting-point particles which are mainly Al2Sm phase. When the mass fraction of Sm is high from 1.5% to 2.0%, the acicular Mg12Nd phase appears in the alloy. With the increase of Sm content within the range from 0 to 2.0%, the tensile strength of alloys at ambient and elevated temperature firstly increases slightly, and then decreases; while the elongation decreases continuously. The tensile fracture of the alloy is quasi-cleavage failure with plastic characteristic.
Microstructures and mechanical properties of Mg-6Al-1.2Y-0.9Nd magnesium alloy with Sm addition were investigated through OM, SEM, EDS and XRD. The results show that Sm combines firstly with Al to form dispersed, high-melting-point particles which are mainly Al2Sm phase. When the mass fraction of Sm is high from 1.5% to 2.0%, the acicular Mg12Nd phase appears in the alloy. With the increase of Sm content within the range from 0 to 2.0%, the tensile strength of alloys at ambient and elevated temperature firstly increases slightly, and then decreases; while the elongation decreases continuously. The tensile fracture of the alloy is quasi-cleavage failure with plastic characteristic.
2010, 39(1):101-105.
Abstract:
With the method of orthogonal experiment, nine kinds of Mg-Nd-Gd-Zn-Zr magnesium alloys with different composition were prepared by sand casting. The cast microstructures and mechanical properties of Mg-Nd-Gd-Zn-Zr magnesium alloys were investigated, and the effects of Gd and Nd element on mechanical properties at room temperature were also studied by analyzing experiment results of mechanical properties. It is found that the as-cast microstructure of Mg-Nd-Gd-Zn-Zr alloys consists of α-Mg grains with Mg12Nd phase in the grain boundary. After the solid solution treatment, almost all of the phases in the grain boundary dissolved in the matrix; however, there was still discontinued Mg12Nd phase in the boundary. The increasing Gd content results in higher ultimate strength, yield strength and elongation. With increasing Nd content, the ultimate strength, the yield strength and the elongation increase. However, the elongation decreases when Nd is over 2.85 wt%. The effects of Nd content on the ultimate strength and yield strength of Mg-Nd-Gd-Zn-Zr alloy at room temperature are more significant than that of Gd. When Zn content is increased, the yield strength increases, but the ultimate strength and the elongation decreases. And Zn content has the greatest impact on elongation.
With the method of orthogonal experiment, nine kinds of Mg-Nd-Gd-Zn-Zr magnesium alloys with different composition were prepared by sand casting. The cast microstructures and mechanical properties of Mg-Nd-Gd-Zn-Zr magnesium alloys were investigated, and the effects of Gd and Nd element on mechanical properties at room temperature were also studied by analyzing experiment results of mechanical properties. It is found that the as-cast microstructure of Mg-Nd-Gd-Zn-Zr alloys consists of α-Mg grains with Mg12Nd phase in the grain boundary. After the solid solution treatment, almost all of the phases in the grain boundary dissolved in the matrix; however, there was still discontinued Mg12Nd phase in the boundary. The increasing Gd content results in higher ultimate strength, yield strength and elongation. With increasing Nd content, the ultimate strength, the yield strength and the elongation increase. However, the elongation decreases when Nd is over 2.85 wt%. The effects of Nd content on the ultimate strength and yield strength of Mg-Nd-Gd-Zn-Zr alloy at room temperature are more significant than that of Gd. When Zn content is increased, the yield strength increases, but the ultimate strength and the elongation decreases. And Zn content has the greatest impact on elongation.
2010, 39(1):106-111.
Abstract:
The hot deformation behavior of ZK60 and ZK60(0.9Y) magnesium alloys was investigated by hot compressive tests on Gleeble-1500 thermal simulation test machine in temperature range from 473 to 723 K and strain rate from 0.001 to 1s-1. The stress exponent and the deformation activation energy were calculated. The constitutive equation of the plastic deformation of ZK60 alloy was obtained by introducing Zener-Hollomon parameter. The results show that the true stress-strain curves of the alloys have dynamic recrystallization character under the present deformation conditions; within the temperature range from 573 to 723 K, the stress exponent increases with the increase of deformation temperature and the increment increases gradually. The deformation activation energy changes with the deformation temperature and strain rate. Compared with the ZK60 alloy, the deformation activation energy of the ZK60(0.9Y) alloy decreases by 30% and the materials constant (n and A) also decrease.
The hot deformation behavior of ZK60 and ZK60(0.9Y) magnesium alloys was investigated by hot compressive tests on Gleeble-1500 thermal simulation test machine in temperature range from 473 to 723 K and strain rate from 0.001 to 1s-1. The stress exponent and the deformation activation energy were calculated. The constitutive equation of the plastic deformation of ZK60 alloy was obtained by introducing Zener-Hollomon parameter. The results show that the true stress-strain curves of the alloys have dynamic recrystallization character under the present deformation conditions; within the temperature range from 573 to 723 K, the stress exponent increases with the increase of deformation temperature and the increment increases gradually. The deformation activation energy changes with the deformation temperature and strain rate. Compared with the ZK60 alloy, the deformation activation energy of the ZK60(0.9Y) alloy decreases by 30% and the materials constant (n and A) also decrease.
2010, 39(1):112-116.
Abstract:
ODS nickel-based superalloys with different contents of Y2O3 (mass fraction from 0% to 10%) as dispersion phase were prepared by powder metallurgy (PM) method by different sintering technologies. Effects of oxide content and sintering temperature on the mechanical properties of ODS nickel-based superalloys were studied. Results reveal that the sample with 1.5% Y2O3 sintered at 1260 °C for 2 h has optimal comprehensive properties, whose relative density is 90.9% and tensile strength is 669 MPa. The phases of alloy powder prepared by different milling technologies were determined by XRD. The mechanism for the effect of Y2O3 content and sintering temperature on the mechanical properties of the ODS superalloys was analyzed through fracture microstructure observation and micro-area chemical composition analysis.
ODS nickel-based superalloys with different contents of Y2O3 (mass fraction from 0% to 10%) as dispersion phase were prepared by powder metallurgy (PM) method by different sintering technologies. Effects of oxide content and sintering temperature on the mechanical properties of ODS nickel-based superalloys were studied. Results reveal that the sample with 1.5% Y2O3 sintered at 1260 °C for 2 h has optimal comprehensive properties, whose relative density is 90.9% and tensile strength is 669 MPa. The phases of alloy powder prepared by different milling technologies were determined by XRD. The mechanism for the effect of Y2O3 content and sintering temperature on the mechanical properties of the ODS superalloys was analyzed through fracture microstructure observation and micro-area chemical composition analysis.
25 Growth Behavior of Cu6Sn5 at the Interface of Sn-2.5Ag-0.7Cu(0.1RE) Solder Joints for Micro-Joining
2010, 39(1):117-121.
Abstract:
The microstructure of low-Ag-content Sn-2.5Ag-0.7Cu(0.1RE)/Cu solder joint interface and growth behavior of Cu6Sn5 intermetallic compound (IMC) were investigated by XRD, SEM and EDAX. The results show that the Cu6Sn5 thickness of the solder joint interface is decided by its dissolution and growing during soldering. With the aging time increasing, the Cu6Sn5 morphology of the solder joint interface changed from scallop-like to lamellar; the growth dynamics follows the parabola law and its growth behavior is controlled by diffusion mechanism. Addition of 0.1% RE (mass fraction) in the Sn-2.5Ag-0.7Cu solder alloy can effectively reduce the growing rate of the solder joint Cu6Sn5 IMC during the soldering and aging period, and change the fracture mechanism of solder joint; therefore the reliability of the solder joint can be greatly improved.
The microstructure of low-Ag-content Sn-2.5Ag-0.7Cu(0.1RE)/Cu solder joint interface and growth behavior of Cu6Sn5 intermetallic compound (IMC) were investigated by XRD, SEM and EDAX. The results show that the Cu6Sn5 thickness of the solder joint interface is decided by its dissolution and growing during soldering. With the aging time increasing, the Cu6Sn5 morphology of the solder joint interface changed from scallop-like to lamellar; the growth dynamics follows the parabola law and its growth behavior is controlled by diffusion mechanism. Addition of 0.1% RE (mass fraction) in the Sn-2.5Ag-0.7Cu solder alloy can effectively reduce the growing rate of the solder joint Cu6Sn5 IMC during the soldering and aging period, and change the fracture mechanism of solder joint; therefore the reliability of the solder joint can be greatly improved.
2010, 39(1):122-125.
Abstract:
Ti and Cu were used as interlayer materials, and the diffusion bonding of Be/CuCrZr alloys were carried out onto Be side by hot isostatic pressing. The four Be samples had different surface roughness. The coating, interface behavior and microstructure of the diffusion bonded alloys were studied by AES, SEM (EDS), room-temperature shear test and XRD. The results show that the Ti coating band (9 μm thickness) and the Cu coating band (35 μm thickness) are homogeneous, and few harmful ingredients are observed. Dual-target and single-side coating technology is favorable to reduce the Ti-coating oxidation. Shearing strength of the Be/CuCrZr interface is increased significantly, with the highest up to 243 MPa. But effect of the different surface roughness on the shearing strength is not obvious. The bonding strength of Be-Ti is high, and all the shear fracture of the samples occurs in the Cu layer.
Ti and Cu were used as interlayer materials, and the diffusion bonding of Be/CuCrZr alloys were carried out onto Be side by hot isostatic pressing. The four Be samples had different surface roughness. The coating, interface behavior and microstructure of the diffusion bonded alloys were studied by AES, SEM (EDS), room-temperature shear test and XRD. The results show that the Ti coating band (9 μm thickness) and the Cu coating band (35 μm thickness) are homogeneous, and few harmful ingredients are observed. Dual-target and single-side coating technology is favorable to reduce the Ti-coating oxidation. Shearing strength of the Be/CuCrZr interface is increased significantly, with the highest up to 243 MPa. But effect of the different surface roughness on the shearing strength is not obvious. The bonding strength of Be-Ti is high, and all the shear fracture of the samples occurs in the Cu layer.
2010, 39(1):126-128.
Abstract:
Magnetocaloric effect of low-purity Gd0.95Nb0.05 alloys after arc-casting and 400 oC, 1 h heat treatment was studied by X-ray diffraction technique, direct magnetocaloric effect measuring instrument and vibrating sample magnetometer (VSM). The results show that proper amount of Nb addition doesn’t change the Curie temperature of Gd but obviously improves its magnetocaloric effect. The maximum adiabatic temperature change of Gd0.95Nb0.05 alloys increases to 3.5 K from 3.1 K in 1.2 T magnetic field, higher than that of commercial low-purity Gd. Meanwhile the maximum magnetic entropy of Gd0.95Nb0.05 alloys reaches to 3.99 J/(kg·K) in 1.5 T magnetic field. After 400 oC, 1 h heat treatment, Curie temperature of Gd0.95Nb0.05 alloys increases by 2 K, the maximum adiabatic temperature change increases to 3.6 K in 1.2 T magnetic field, and the maximum magnetic entropy also increases to 4.09 J/(kg·K) in 1.5 T magnetic field. Gd0.95Nb0.05 alloys are a potential candidate of magnetic cooling materials with relatively low cost in commercial field.
Magnetocaloric effect of low-purity Gd0.95Nb0.05 alloys after arc-casting and 400 oC, 1 h heat treatment was studied by X-ray diffraction technique, direct magnetocaloric effect measuring instrument and vibrating sample magnetometer (VSM). The results show that proper amount of Nb addition doesn’t change the Curie temperature of Gd but obviously improves its magnetocaloric effect. The maximum adiabatic temperature change of Gd0.95Nb0.05 alloys increases to 3.5 K from 3.1 K in 1.2 T magnetic field, higher than that of commercial low-purity Gd. Meanwhile the maximum magnetic entropy of Gd0.95Nb0.05 alloys reaches to 3.99 J/(kg·K) in 1.5 T magnetic field. After 400 oC, 1 h heat treatment, Curie temperature of Gd0.95Nb0.05 alloys increases by 2 K, the maximum adiabatic temperature change increases to 3.6 K in 1.2 T magnetic field, and the maximum magnetic entropy also increases to 4.09 J/(kg·K) in 1.5 T magnetic field. Gd0.95Nb0.05 alloys are a potential candidate of magnetic cooling materials with relatively low cost in commercial field.
28 Preparation and Properties of Nano-Sized SiC Particles Reinforced AZ91D Magnesium Matrix Composites
2010, 39(1):134-138.
Abstract:
Magnesium matrix composites reinforced with nano-sized SiC particles (n-SiCp/AZ91D) were fabricated by high intensity ultrasonic assisted casting. The microstructure of the nanocomposites was investigated by optical microscopy, scanning electronic microscopy (SEM) methods and room-temperature mechanical properties were measured using a universal electronic material tester. The results showed that n-SiCp addition can refine the grains, and the distribution of n-SiCp in magnesium alloy melts is significantly improved by ultrasonic processing. Compared with the unreinforced AZ91D matrix, mechanical properties of the nanocomposites including tensile and yield strengths and hardness are remarkably improved; in particular the yield strength is increased by 57% after gravity permanent mould casting.
Magnesium matrix composites reinforced with nano-sized SiC particles (n-SiCp/AZ91D) were fabricated by high intensity ultrasonic assisted casting. The microstructure of the nanocomposites was investigated by optical microscopy, scanning electronic microscopy (SEM) methods and room-temperature mechanical properties were measured using a universal electronic material tester. The results showed that n-SiCp addition can refine the grains, and the distribution of n-SiCp in magnesium alloy melts is significantly improved by ultrasonic processing. Compared with the unreinforced AZ91D matrix, mechanical properties of the nanocomposites including tensile and yield strengths and hardness are remarkably improved; in particular the yield strength is increased by 57% after gravity permanent mould casting.
2010, 39(1):139-143.
Abstract:
By means of adding micron Ni powder in the Friction Stir Processing (FSP) period and the resultant rapid in-situ reaction between Al and Ni under FSP condition, Al3Ni-Al composites were obtained on Al alloy 1100-H14 surface layer. The microstructures of the surface composites were analyzed by SEM and EDS, the phase composition was examined by XRD, and the microhardness was also measured. Results show that Ni powder was broken sufficiently under the severe thermal-mechanical coupling of FSP, and the broken Ni in-situ reacted with Al matrix rapidly to produce sub-micron or even nano particles of Al3Ni; while a few micron particles of residual Ni were covered by Al3Ni layer and homogeneously distributed in Al matrix with fine Al3Ni particles. Therefore, the microhardness of the composites increased greatly and reached to 818.3 MPa, 2.4 times of that of Al alloy 1100-H14.
By means of adding micron Ni powder in the Friction Stir Processing (FSP) period and the resultant rapid in-situ reaction between Al and Ni under FSP condition, Al3Ni-Al composites were obtained on Al alloy 1100-H14 surface layer. The microstructures of the surface composites were analyzed by SEM and EDS, the phase composition was examined by XRD, and the microhardness was also measured. Results show that Ni powder was broken sufficiently under the severe thermal-mechanical coupling of FSP, and the broken Ni in-situ reacted with Al matrix rapidly to produce sub-micron or even nano particles of Al3Ni; while a few micron particles of residual Ni were covered by Al3Ni layer and homogeneously distributed in Al matrix with fine Al3Ni particles. Therefore, the microhardness of the composites increased greatly and reached to 818.3 MPa, 2.4 times of that of Al alloy 1100-H14.
2010, 39(1):144-148.
Abstract:
Effects of solid solution heat treatment and aging heat treatment on high purity Al-Cu-Mg-Ag alloys with trace Mn and Zr were investigated. Results show that when the alloys are solid solution treated at 520-525 ℃, the mechanical properties reach up to a relatively high level, and the solid solution time has little effect on the properties. The time to reach peak aging is about 12 h at 160 ℃ but only 4 h at 180 ℃. Adding trace Mn and Zr could increase the elongation of Al-Cu-Mg-Ag alloys greatly. However, Mn element could decrease the tensile strength while Zr could increase it significantly. Both Mn and Zr elements can improve the heat resistance of Al-Cu-Mg-Ag alloys markedly.
Effects of solid solution heat treatment and aging heat treatment on high purity Al-Cu-Mg-Ag alloys with trace Mn and Zr were investigated. Results show that when the alloys are solid solution treated at 520-525 ℃, the mechanical properties reach up to a relatively high level, and the solid solution time has little effect on the properties. The time to reach peak aging is about 12 h at 160 ℃ but only 4 h at 180 ℃. Adding trace Mn and Zr could increase the elongation of Al-Cu-Mg-Ag alloys greatly. However, Mn element could decrease the tensile strength while Zr could increase it significantly. Both Mn and Zr elements can improve the heat resistance of Al-Cu-Mg-Ag alloys markedly.
Chen Yu’an
,
Huang Hua
,
Fu Jie
,
Guo Qing
,
Pan Fusheng
,
Deng Shiping
,
Li Jiaming
,
Zhao Guangming
2010, 39(1):149-152.
Abstract:
Mg2Ni1-xCux alloys (x=0, 0.2, 0.4) were synthesized by two steps: induction melting and then ball milling. The composition and microstructure of the alloys were analyzed by XRD and SEM/EDX, respectively. Mg2Ni phase was observed in all of the 3 alloys. The increase of Cu amount led to the formation of Mg2Cu phase and Cu11Mg10Ni9 phase. The hydrogen absorption/desorption properties were tested on PCT measurement apparatus, and the results show that the hydrogen absorption/desorption properties of the alloys can be improved by the addition of Cu.
Mg2Ni1-xCux alloys (x=0, 0.2, 0.4) were synthesized by two steps: induction melting and then ball milling. The composition and microstructure of the alloys were analyzed by XRD and SEM/EDX, respectively. Mg2Ni phase was observed in all of the 3 alloys. The increase of Cu amount led to the formation of Mg2Cu phase and Cu11Mg10Ni9 phase. The hydrogen absorption/desorption properties were tested on PCT measurement apparatus, and the results show that the hydrogen absorption/desorption properties of the alloys can be improved by the addition of Cu.
2010, 39(1):153-156.
Abstract:
Aqueously well-dispersed NiPd nanoparticles with a dimension of about 30 nm were prepared by a modified polyol reduction process, using glycol as both solvent and reductant, and PVP as stabilizing agent. The as-synthesized nanoparticles with different composition were characterized by XRD, ICP and TEM. It is proved that the nanoparticles are NiPd alloy, and the PVP prevents them from agglomeration and oxidation. The magnetic properties and heat effect under external alternating magnetic field reveal that the obtained NiPd nanoalloy is ferromagnetic material and has bigger coercive force; additionally, the saturation magnetization and heat generation ability of the nanoalloy are improved by the increasing of Ni content. When the nanoparticles were exposed to an external alternation magnetic field of 60 kHz and 7.5 kA/m, the samples show high heat generation ability, with the suspension temperature increasing by 14 ℃.
Aqueously well-dispersed NiPd nanoparticles with a dimension of about 30 nm were prepared by a modified polyol reduction process, using glycol as both solvent and reductant, and PVP as stabilizing agent. The as-synthesized nanoparticles with different composition were characterized by XRD, ICP and TEM. It is proved that the nanoparticles are NiPd alloy, and the PVP prevents them from agglomeration and oxidation. The magnetic properties and heat effect under external alternating magnetic field reveal that the obtained NiPd nanoalloy is ferromagnetic material and has bigger coercive force; additionally, the saturation magnetization and heat generation ability of the nanoalloy are improved by the increasing of Ni content. When the nanoparticles were exposed to an external alternation magnetic field of 60 kHz and 7.5 kA/m, the samples show high heat generation ability, with the suspension temperature increasing by 14 ℃.
2010, 39(1):157-161.
Abstract:
Crack propagation rates of FGH96 P/M superalloys with different heat treatments were tested and compared under fatigue/creep interaction at 650 ℃ in air. Influence of heat treatments on the crack propagation rates of FGH96 P/M superalloys was investigated. The results indicate that the crack propagation rates were decreased when increasing the solid solution temperature or salt bath temperature; the effect of solid solution temperature was greater than that of salt bath temperature. Lower aging temperature and shorter aging time also delayed the crack propagation rates; the effect of the aging temperature was greater than that of the aging time. In addition, the crack propagation rates were increased with the dwelling time prolonging, and its effect decreased with the aging temperature increasing.
Crack propagation rates of FGH96 P/M superalloys with different heat treatments were tested and compared under fatigue/creep interaction at 650 ℃ in air. Influence of heat treatments on the crack propagation rates of FGH96 P/M superalloys was investigated. The results indicate that the crack propagation rates were decreased when increasing the solid solution temperature or salt bath temperature; the effect of solid solution temperature was greater than that of salt bath temperature. Lower aging temperature and shorter aging time also delayed the crack propagation rates; the effect of the aging temperature was greater than that of the aging time. In addition, the crack propagation rates were increased with the dwelling time prolonging, and its effect decreased with the aging temperature increasing.
2010, 39(1):162-168.
Abstract:
Fe-Co-B-Si-Nb-Cr bulk amorphous alloys with critical diameters up to 4 mm were prepared by copper mold casting method using micro-alloying technology. The glass-forming ability (GFA) and soft magnetic properties of the obtained bulk amorphous alloys were characterized by means of XRD, TEM, DSC, DTA and VSM. Corrosion and mechanical properties of bulk amorphous alloys were measured using potentiodynamic polarization, macro compressive experiment and nanoindentation testing techniques. The results show that the addition of Cr element slightly decreases GFA of Fe-Co-B-Si-Nb alloys, but is very effective in increasing corrosion resistance and improving mechanical properties and soft magnetic properties for the glassy alloys. The copper-mold-cast alloys exhibit high GFA with diameters up to 4 mm. These Fe-based bulk amorphous alloys exhibit high saturation magnetization of 0.81-1.04 T, extremely low coercive force of 0.6~1.6 A/m, Yong’s modulus of 200-215 GPa, elastic strain of about 2% and plastic strain of 0.7%, and they also possess ultrahigh fracture strength of 3840-4043 MPa. The plastic deformation of the {[(Fe0.6Co0.4)0.75B0.2Si0.05]0.96Nb0.04}96Cr4 bulk amorphous alloy at room temperature was studied by depth-sensing nanoindentation technique. It is shown that the deformation behavior of the bulk amorphous alloys depends on the applied loading rate during nanoindentation. Distinct serrated flow was observed in the loading rate range from 0.75 to 3 mN/s. However, it disappeared at a loading rate of 6 mN/s. Furthermore, corrosion measurements show that corrosion rate and corrosion current density of the bulk amorphous alloys in 0.5 mol/L NaCl solution decrease from 7.0×10-1 to 1.6×10-3 mm/y and from 3.9×10-6 to 8.7×10-7 A/cm2, respectively, with increasing Cr content from x=0 to x=4(at%).
Fe-Co-B-Si-Nb-Cr bulk amorphous alloys with critical diameters up to 4 mm were prepared by copper mold casting method using micro-alloying technology. The glass-forming ability (GFA) and soft magnetic properties of the obtained bulk amorphous alloys were characterized by means of XRD, TEM, DSC, DTA and VSM. Corrosion and mechanical properties of bulk amorphous alloys were measured using potentiodynamic polarization, macro compressive experiment and nanoindentation testing techniques. The results show that the addition of Cr element slightly decreases GFA of Fe-Co-B-Si-Nb alloys, but is very effective in increasing corrosion resistance and improving mechanical properties and soft magnetic properties for the glassy alloys. The copper-mold-cast alloys exhibit high GFA with diameters up to 4 mm. These Fe-based bulk amorphous alloys exhibit high saturation magnetization of 0.81-1.04 T, extremely low coercive force of 0.6~1.6 A/m, Yong’s modulus of 200-215 GPa, elastic strain of about 2% and plastic strain of 0.7%, and they also possess ultrahigh fracture strength of 3840-4043 MPa. The plastic deformation of the {[(Fe0.6Co0.4)0.75B0.2Si0.05]0.96Nb0.04}96Cr4 bulk amorphous alloy at room temperature was studied by depth-sensing nanoindentation technique. It is shown that the deformation behavior of the bulk amorphous alloys depends on the applied loading rate during nanoindentation. Distinct serrated flow was observed in the loading rate range from 0.75 to 3 mN/s. However, it disappeared at a loading rate of 6 mN/s. Furthermore, corrosion measurements show that corrosion rate and corrosion current density of the bulk amorphous alloys in 0.5 mol/L NaCl solution decrease from 7.0×10-1 to 1.6×10-3 mm/y and from 3.9×10-6 to 8.7×10-7 A/cm2, respectively, with increasing Cr content from x=0 to x=4(at%).
2010, 39(1):169-172.
Abstract:
High-purity nano-crystal Mg(OH)2 powder was prepared, using self-made high-purity MgSO4 and mixed alkali solution of ammonia water and NaOH liquor as starting materials. The effects of several key factors on precipitation rate of Mg and average particle size of powder were studied. The results show that with increasing of initial concentration of Mg2+ and reaction temperature, the precipitation rate of Mg increases, while the average particle size of powder decreases at first, and then increases; if prolong the reaction time and ageing time, the precipitation rate of Mg and the average particle size of powder both increase; if increase stirring rate, the precipitation rate of Mg does not increase obviously, but the average particle size of powder decreases. When the initial concentration of Mg2+ is 2.0 mol×L-1, reaction temperature is 50 oC, reaction time is 60 min, stirring rate is 900 r×min-1, and ageing time 90 min, the precipitation rate of Mg is 95.4%; meanwhile the morphology of obtained Mg(OH)2 particles is hexagonal flake, the size of them is between 50 nm and 140 nm, the granularity distribution is uniform, the dispersibility is good, and the purity is high.
High-purity nano-crystal Mg(OH)2 powder was prepared, using self-made high-purity MgSO4 and mixed alkali solution of ammonia water and NaOH liquor as starting materials. The effects of several key factors on precipitation rate of Mg and average particle size of powder were studied. The results show that with increasing of initial concentration of Mg2+ and reaction temperature, the precipitation rate of Mg increases, while the average particle size of powder decreases at first, and then increases; if prolong the reaction time and ageing time, the precipitation rate of Mg and the average particle size of powder both increase; if increase stirring rate, the precipitation rate of Mg does not increase obviously, but the average particle size of powder decreases. When the initial concentration of Mg2+ is 2.0 mol×L-1, reaction temperature is 50 oC, reaction time is 60 min, stirring rate is 900 r×min-1, and ageing time 90 min, the precipitation rate of Mg is 95.4%; meanwhile the morphology of obtained Mg(OH)2 particles is hexagonal flake, the size of them is between 50 nm and 140 nm, the granularity distribution is uniform, the dispersibility is good, and the purity is high.
2010, 39(1):173-176.
Abstract:
The perovskite La1-xSrxMnO3 nano thin-film on the slide glass basis were prepared by sol-gel method and dip-coating technology. The heat decomposition of the precursor gel was analyzed by means of TG/DTA. The appearance characteristic of the thin film was observed by AFM. The phase change was analyzed by XRD and crystal grain size was also calculated. The results show that the perovskite La1-xSrxMnO3 thin film can be synthesized at 600 °C and average crystal grain size is 10.349 nm. The degradation experiment of various water-soluble dyestuffs was performed using the film as photo-catalyst. The results reveal that this nano thin-film with Sr doping has good photo-catalysis and when x=0.2 the effect is best.
The perovskite La1-xSrxMnO3 nano thin-film on the slide glass basis were prepared by sol-gel method and dip-coating technology. The heat decomposition of the precursor gel was analyzed by means of TG/DTA. The appearance characteristic of the thin film was observed by AFM. The phase change was analyzed by XRD and crystal grain size was also calculated. The results show that the perovskite La1-xSrxMnO3 thin film can be synthesized at 600 °C and average crystal grain size is 10.349 nm. The degradation experiment of various water-soluble dyestuffs was performed using the film as photo-catalyst. The results reveal that this nano thin-film with Sr doping has good photo-catalysis and when x=0.2 the effect is best.
2010, 39(1):177-181.
Abstract:
IT-SOFC composite anode material Ce0.8Ca0.2O2-La0.7Sr0.3Cr0.5Mn0.5-xCoxO3-δ (CDC-LSCMCo) was synthesized in one-step by glycine nitrate process (GNP). The results from X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) indicate that the composite anode powder with single fluorite-perovskite phase and small grain size (about 1 μm) was obtained after sintering the predecessor at 1350 oC for 5 h. Conductivity testing show that the conductivity of CDC-LSCMCo increases with the Co content increasing when the temperature is above 750 oC; while at 800 oC the conductivity is 10.5 S·cm-1 and 0.7 S·cm-1 in air and H2 atmosphere, respectively. Good chemical-thermal compatibility between CDC-LSCMCo and La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) was confirmed via XRD and SEM. CDC-LSCMCo is a promising anode material of SOFC for its excellent properties at intermediate temperature.
IT-SOFC composite anode material Ce0.8Ca0.2O2-La0.7Sr0.3Cr0.5Mn0.5-xCoxO3-δ (CDC-LSCMCo) was synthesized in one-step by glycine nitrate process (GNP). The results from X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) indicate that the composite anode powder with single fluorite-perovskite phase and small grain size (about 1 μm) was obtained after sintering the predecessor at 1350 oC for 5 h. Conductivity testing show that the conductivity of CDC-LSCMCo increases with the Co content increasing when the temperature is above 750 oC; while at 800 oC the conductivity is 10.5 S·cm-1 and 0.7 S·cm-1 in air and H2 atmosphere, respectively. Good chemical-thermal compatibility between CDC-LSCMCo and La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) was confirmed via XRD and SEM. CDC-LSCMCo is a promising anode material of SOFC for its excellent properties at intermediate temperature.
2010, 39(1):182-188.
Abstract:
Recent research progress of inorganic sulfides electrode materials for lithium-ion batteries，including binary metal sulfides, oxysulfides, Chevrel phase compounds, thiospinels and thio-phosphates, is summarized. The prospect of the electrode materials in future is previewed. Thio-phosphates and other polyanion sulfides are considered as promising electrode materials.
Recent research progress of inorganic sulfides electrode materials for lithium-ion batteries，including binary metal sulfides, oxysulfides, Chevrel phase compounds, thiospinels and thio-phosphates, is summarized. The prospect of the electrode materials in future is previewed. Thio-phosphates and other polyanion sulfides are considered as promising electrode materials.
