Volume 43,Issue 6,2014 Table of Contents
2014, 43(6):1281-1285.
Abstract:
The as-cast Mg-9Li-3Al-2.5Sr (LAJ932) alloy ingots with diameters of 10 mm and 90 mm were prepared. The extrusion of Φ90 mm as-cast LAJ932 alloy ingot was carried out at 533 K with an extrusion ratio of 28. The microstructure and the mechanical properties of the as-cast and extruded LAJ932 alloys were discussed. The microstructure evolution during extrusion was analyzed. The results show that both the as-cast and the extruded LAJ932 alloys contain hcp α-Mg, bcc β-Li and Al4Sr phase. The grain size of as-cast Φ10 mm specimen is smaller than that of Φ90 mm specimen. The microstructure evolution during extrusion is governed by continuous dynamic recrystallization (CDRX) in α-Mg phase whereas discontinuous dynamic recrystallization (DDRX) occurs in β-Li phase. {100}<100> texture is formed in the hcp α-Mg phase whereas {110}<101> texture is formed in the bcc β-Li phase during the extrusion process. Both the strength and the ductility of the LAJ932 alloy is improved by extrusion. The extruded LAJ932 alloy shows a favorable combination of the strength and the ductility with the tensile strength of 235 MPa, yield strength of 221 MPa and the elongation of 19.4%.
The as-cast Mg-9Li-3Al-2.5Sr (LAJ932) alloy ingots with diameters of 10 mm and 90 mm were prepared. The extrusion of Φ90 mm as-cast LAJ932 alloy ingot was carried out at 533 K with an extrusion ratio of 28. The microstructure and the mechanical properties of the as-cast and extruded LAJ932 alloys were discussed. The microstructure evolution during extrusion was analyzed. The results show that both the as-cast and the extruded LAJ932 alloys contain hcp α-Mg, bcc β-Li and Al4Sr phase. The grain size of as-cast Φ10 mm specimen is smaller than that of Φ90 mm specimen. The microstructure evolution during extrusion is governed by continuous dynamic recrystallization (CDRX) in α-Mg phase whereas discontinuous dynamic recrystallization (DDRX) occurs in β-Li phase. {100}<100> texture is formed in the hcp α-Mg phase whereas {110}<101> texture is formed in the bcc β-Li phase during the extrusion process. Both the strength and the ductility of the LAJ932 alloy is improved by extrusion. The extruded LAJ932 alloy shows a favorable combination of the strength and the ductility with the tensile strength of 235 MPa, yield strength of 221 MPa and the elongation of 19.4%.
2014, 43(6):1286-1290.
Abstract:
The AlCrMoNiTi high entropy alloy was prepared by powder metallurgy process. Its microstructure and hardness of as-cast and annealed state were studied. The results show that the as-cast alloy exhibits a mixture of the dendrite (Cr, Mo)-rich bcc phase and the interdendrite (Al, Ni, Ti)-rich fcc phase. The aged alloy can obtain a peak hardness HV of 6150 MPa at 900 oC, and then anneal softening occurs at 1000 oC, but its hardness HV still maintained at a high level of 5160 MPa. This shows that the AlCrMoNiTi alloy exhibits a good high-temperature age hardening performance. Age hardening of the alloy is mainly attributed to the grain refinement strengthening at 800 oC and the precipitation hardening of the second phase (bcc2) at 900 oC. The disappeared second phase and grain coarsening are the main reasons for the softening anneal at 1000 oC.
The AlCrMoNiTi high entropy alloy was prepared by powder metallurgy process. Its microstructure and hardness of as-cast and annealed state were studied. The results show that the as-cast alloy exhibits a mixture of the dendrite (Cr, Mo)-rich bcc phase and the interdendrite (Al, Ni, Ti)-rich fcc phase. The aged alloy can obtain a peak hardness HV of 6150 MPa at 900 oC, and then anneal softening occurs at 1000 oC, but its hardness HV still maintained at a high level of 5160 MPa. This shows that the AlCrMoNiTi alloy exhibits a good high-temperature age hardening performance. Age hardening of the alloy is mainly attributed to the grain refinement strengthening at 800 oC and the precipitation hardening of the second phase (bcc2) at 900 oC. The disappeared second phase and grain coarsening are the main reasons for the softening anneal at 1000 oC.
2014, 43(6):1291-1295.
Abstract:
The microstructures of the as-cast Mg-5Sn alloys with 0.5wt%, 1wt%, and 2wt% Cu addition were characterized by XRD and SEM. The results show that besides α-Mg and Mg2Sn phase, Mg2Cu appears in the Cu containing alloys. The addition of Cu results in obvious grain refinement. With Cu content increasing, the amounts of Mg2Sn and Mg2Cu increase, but the sizes of these two intermetallics coarsen. The tensile test at the ambient temperature shows that when Cu content is in the range of 0.5wt%~1.0wt%, the Cu addition helps to improve the strength of the alloys; however, excessive Cu addition leads to the deterioration of the ultimate strength. The optimum mechanical property is attained at Mg-5Sn-1.0Cu alloy, where the UTS and the elongation reach 180 MPa and 12%, respectively. The behavior of the Mg-Sn-Cu alloy in the compressive creep at 175 °C at applied load of 35~75 MPa was also investigated, which shows that the Cu addition helps to improve the compressive creep resistance of Mg-Sn alloy.
The microstructures of the as-cast Mg-5Sn alloys with 0.5wt%, 1wt%, and 2wt% Cu addition were characterized by XRD and SEM. The results show that besides α-Mg and Mg2Sn phase, Mg2Cu appears in the Cu containing alloys. The addition of Cu results in obvious grain refinement. With Cu content increasing, the amounts of Mg2Sn and Mg2Cu increase, but the sizes of these two intermetallics coarsen. The tensile test at the ambient temperature shows that when Cu content is in the range of 0.5wt%~1.0wt%, the Cu addition helps to improve the strength of the alloys; however, excessive Cu addition leads to the deterioration of the ultimate strength. The optimum mechanical property is attained at Mg-5Sn-1.0Cu alloy, where the UTS and the elongation reach 180 MPa and 12%, respectively. The behavior of the Mg-Sn-Cu alloy in the compressive creep at 175 °C at applied load of 35~75 MPa was also investigated, which shows that the Cu addition helps to improve the compressive creep resistance of Mg-Sn alloy.
2014, 43(6):1296-1299.
Abstract:
Vertically aligned ZnO nanowire array (NWA) was synthesized on the transparent conductive substrates by a facile hydrothermal method. Then, TiO2 nanotube array (NTA) was obtained by a successive treatment of the ZnO NWA. Moreover, two dye-sensitized solar cells (DSSCs) were fabricated using these samples as the photoanodes in order to investigate their photoelectrochemical performance. It is found that TiO2 NTA demonstrates a power conversion efficiency of ~0.81 %, which is three times higher than ZnO NWA. The DSSC devices were used with a simple diode model to evaluate the current-voltage (J-V) curves. Finally, it was revealed that the cell performance improvement is attributed to an increased shuttle resistance and a suppressed leakage current.
Vertically aligned ZnO nanowire array (NWA) was synthesized on the transparent conductive substrates by a facile hydrothermal method. Then, TiO2 nanotube array (NTA) was obtained by a successive treatment of the ZnO NWA. Moreover, two dye-sensitized solar cells (DSSCs) were fabricated using these samples as the photoanodes in order to investigate their photoelectrochemical performance. It is found that TiO2 NTA demonstrates a power conversion efficiency of ~0.81 %, which is three times higher than ZnO NWA. The DSSC devices were used with a simple diode model to evaluate the current-voltage (J-V) curves. Finally, it was revealed that the cell performance improvement is attributed to an increased shuttle resistance and a suppressed leakage current.
2014, 43(6):1300-1303.
Abstract:
Isothermal hot compression tests of annealed Al-14Cu-7Ce alloy were carried out on Gleeble-3500 system in the temperature range from 573 K to 823 K and the stain rate range from 0.001 s-1 to 1 s-1. The resulted true stress-true strain data were employed to establish a constitutive equation for predicting high temperature flow stress. The results show that the flow stress follow well the rate equation . The effect of strain was taken into account by fitting of polynomials into the material parameters A, αL and n. The proposed constitutive equation can predict precisely high temperature flow stress of Al-14Cu-7Ce alloy. The control mechanism of hot deformation is dislocation climb.
Isothermal hot compression tests of annealed Al-14Cu-7Ce alloy were carried out on Gleeble-3500 system in the temperature range from 573 K to 823 K and the stain rate range from 0.001 s-1 to 1 s-1. The resulted true stress-true strain data were employed to establish a constitutive equation for predicting high temperature flow stress. The results show that the flow stress follow well the rate equation . The effect of strain was taken into account by fitting of polynomials into the material parameters A, αL and n. The proposed constitutive equation can predict precisely high temperature flow stress of Al-14Cu-7Ce alloy. The control mechanism of hot deformation is dislocation climb.
2014, 43(6):1304-1307.
Abstract:
The anti-perovskite manganese nitrides with the general formula Mn3Ga1-xSnxN (x=0, 0.1, 0.2, 0.3, 0.4) were fabricated by mechanical ball milling followed by spark plasma sintering (SPS). The temperature dependence of thermal expansion, thermal conductivity and mechanical properties were investigated. The results show that the negative thermal expansion (NTE) operation-temperature window shifts toward higher temperature with increasing of Sn concentration. Typically, the linear NTE coefficient of the Mn3Ga0.9Sn0.1N compound reaches as much as –27.5×10-6 K-1, with an operation-temperature window of 59 K from 279 to 338 K. In addition, the coefficient of thermal expansion (CTE) of Mn3Ga0.6Sn0.4N is very low in the temperature range of 363~400 K. The value of thermal conductivity of this material is about 3.2 W·(m·K)-1 around room temperature. Compression test indicates that the compressive strength is about 210 MPa. This NTE material may possibly be exploited to design the critical components for space applications.
The anti-perovskite manganese nitrides with the general formula Mn3Ga1-xSnxN (x=0, 0.1, 0.2, 0.3, 0.4) were fabricated by mechanical ball milling followed by spark plasma sintering (SPS). The temperature dependence of thermal expansion, thermal conductivity and mechanical properties were investigated. The results show that the negative thermal expansion (NTE) operation-temperature window shifts toward higher temperature with increasing of Sn concentration. Typically, the linear NTE coefficient of the Mn3Ga0.9Sn0.1N compound reaches as much as –27.5×10-6 K-1, with an operation-temperature window of 59 K from 279 to 338 K. In addition, the coefficient of thermal expansion (CTE) of Mn3Ga0.6Sn0.4N is very low in the temperature range of 363~400 K. The value of thermal conductivity of this material is about 3.2 W·(m·K)-1 around room temperature. Compression test indicates that the compressive strength is about 210 MPa. This NTE material may possibly be exploited to design the critical components for space applications.
2014, 43(6):1308-1311.
Abstract:
Nickel-based alloy closed-pore hollow spheres were fabricated using three kinds of powders with different particle sizes by powder metallurgy process. The diameter of the sphere is about 3~3.5 mm and the wall thickness is 0.3~0.4 mm. The optimum slurry ratio is the liquid-solid ratio of 1/2. Some performances of metal hollow sphere (MHS) materials made of the powders with different particle sizes were discussed. The results show that the porosity decreases, density increases with the gradual decrease of particle size; in the meantime the compression strength of MHS increases from 16 to 18 MPa and then to 28 MPa, and actual relative compression strength value is only 50% of the theory value.
Nickel-based alloy closed-pore hollow spheres were fabricated using three kinds of powders with different particle sizes by powder metallurgy process. The diameter of the sphere is about 3~3.5 mm and the wall thickness is 0.3~0.4 mm. The optimum slurry ratio is the liquid-solid ratio of 1/2. Some performances of metal hollow sphere (MHS) materials made of the powders with different particle sizes were discussed. The results show that the porosity decreases, density increases with the gradual decrease of particle size; in the meantime the compression strength of MHS increases from 16 to 18 MPa and then to 28 MPa, and actual relative compression strength value is only 50% of the theory value.
2014, 43(6):1329-1331.
Abstract:
Ta-doped CeO2 buffer layers were grown on the home-made textured Ni-5W substrates for YBCO coated conductors by a simple metal-organic deposition technique. The characterization of the samples was discussed. XPS results indicate that Ta5+ is reduced into Ta4+ prior to Ce4+, which is helpful to suppress the formation of holes and cracks in CeO2 films from reducing Ce4+ into Ce3+. Additionally, no new phase is found by doping Ta into CeO2, which indicates that Ta4+ replaces the Ce4+ position in CeO2 lattice to form Ce0.75Ta0.25O2. The Ce0.75Ta0.25O2 has a good out-of-plane and in-plane texture FWHM values for ω scan and j scan are 4.38o and 6.67o, respectively. AES measurements show that no Ni element is detected on the surface of Ce0.75Ta0.25O2 film, and a one-layer film has a thickness of about 70 nm. It is promising that the presently developed Ce0.75Ta0.25O2 film can be used as a single multi-functional buffer layer for coated conductor.
Ta-doped CeO2 buffer layers were grown on the home-made textured Ni-5W substrates for YBCO coated conductors by a simple metal-organic deposition technique. The characterization of the samples was discussed. XPS results indicate that Ta5+ is reduced into Ta4+ prior to Ce4+, which is helpful to suppress the formation of holes and cracks in CeO2 films from reducing Ce4+ into Ce3+. Additionally, no new phase is found by doping Ta into CeO2, which indicates that Ta4+ replaces the Ce4+ position in CeO2 lattice to form Ce0.75Ta0.25O2. The Ce0.75Ta0.25O2 has a good out-of-plane and in-plane texture FWHM values for ω scan and j scan are 4.38o and 6.67o, respectively. AES measurements show that no Ni element is detected on the surface of Ce0.75Ta0.25O2 film, and a one-layer film has a thickness of about 70 nm. It is promising that the presently developed Ce0.75Ta0.25O2 film can be used as a single multi-functional buffer layer for coated conductor.
2014, 43(6):1332-1336.
Abstract:
The fatigue crack growth of 2124-T851 aluminum alloy was investigated by Electron Backscatter Diffraction (EBSD) analysis. The result shows that the mode of fatigue crack growth is mainly transcrystalline, and the preferential orientation changes with the difference of grain orientation. When the crack extends to the grain boundary, the deflection of the crack against the normal extensive path will take place as a result of the misorientation of adjoining grains, but the deflection of the crack in the grain inner is mainly caused by the coarse second phase particles which are poor in coordination of deformability under cyclic stress. The phenomenon of bifurcation during the process of the crack propagation is relative with the specific crystallographic direction, which is caused by the simultaneous movement of numerous equivalent {111}<110> slip system on crack-tip.
The fatigue crack growth of 2124-T851 aluminum alloy was investigated by Electron Backscatter Diffraction (EBSD) analysis. The result shows that the mode of fatigue crack growth is mainly transcrystalline, and the preferential orientation changes with the difference of grain orientation. When the crack extends to the grain boundary, the deflection of the crack against the normal extensive path will take place as a result of the misorientation of adjoining grains, but the deflection of the crack in the grain inner is mainly caused by the coarse second phase particles which are poor in coordination of deformability under cyclic stress. The phenomenon of bifurcation during the process of the crack propagation is relative with the specific crystallographic direction, which is caused by the simultaneous movement of numerous equivalent {111}<110> slip system on crack-tip.
2014, 43(6):1342-1346.
Abstract:
The fatigue crack propagation behavior was investigated for the TC4-DT titanium alloy with bimodal and lamellar microstructure, developed by (a+b) annealing treatment and b annealing treatment, respectively. The effect of microstructure on fatigue crack growth rates of TC4-DT titanium alloy has been discussed by SEM analyses of fracture morphology and crack propagation paths in the two different microstructures. The results show that for the bimodal microstructure, the fatigue crack growth rate lowers with decrease in the content of primary a phase, and the turning point in the curve tends to move to the right. The lamellar microstructure exhibits tortuous crack paths and fatigue crack propagation resistance, which indicates that the lamellar structure has better damage tolerance compared with bimodal structure.
The fatigue crack propagation behavior was investigated for the TC4-DT titanium alloy with bimodal and lamellar microstructure, developed by (a+b) annealing treatment and b annealing treatment, respectively. The effect of microstructure on fatigue crack growth rates of TC4-DT titanium alloy has been discussed by SEM analyses of fracture morphology and crack propagation paths in the two different microstructures. The results show that for the bimodal microstructure, the fatigue crack growth rate lowers with decrease in the content of primary a phase, and the turning point in the curve tends to move to the right. The lamellar microstructure exhibits tortuous crack paths and fatigue crack propagation resistance, which indicates that the lamellar structure has better damage tolerance compared with bimodal structure.
2014, 43(6):1347-1351.
Abstract:
In order to assess service properties of 2124-T851 aluminum alloy thick plate in short transverse orientation (S direction) under ultra-high loading, the extremely low cycle fatigue (ELCF) behavior was investigated by controlling nominal axial strain in fatigue experiments of hourglass-type specimens. The results indicate that the 2124-T851 thick plate in S direction exhibits stable cyclic softening in cyclic stress-strain hysteresis loop, and the softening rate can be expressed as a typical?power function of the nominal strain amplitude (Δεn/2). Manson-Coffin formula expressed in Δεn/2 has a good prediction of the ELCF life as compared with the experimental results. The fracture morphology shows that the crack propagation direction tends to follow longitudinal-transverse direction (T direction) in both the monotonic tensile samples and the ELCF fracture samples. With the decrease of Δεn/2, the fracture mode gradually changes from shear mode into normal mode. ELCF microscopic morphology generally?exhibits hybrid fracture?characteristics?of?dimples and extrusion flat caused by two crack surface peened each other. The fatigue striations were found only when Δεn/2 decreased to 0.4%.
In order to assess service properties of 2124-T851 aluminum alloy thick plate in short transverse orientation (S direction) under ultra-high loading, the extremely low cycle fatigue (ELCF) behavior was investigated by controlling nominal axial strain in fatigue experiments of hourglass-type specimens. The results indicate that the 2124-T851 thick plate in S direction exhibits stable cyclic softening in cyclic stress-strain hysteresis loop, and the softening rate can be expressed as a typical?power function of the nominal strain amplitude (Δεn/2). Manson-Coffin formula expressed in Δεn/2 has a good prediction of the ELCF life as compared with the experimental results. The fracture morphology shows that the crack propagation direction tends to follow longitudinal-transverse direction (T direction) in both the monotonic tensile samples and the ELCF fracture samples. With the decrease of Δεn/2, the fracture mode gradually changes from shear mode into normal mode. ELCF microscopic morphology generally?exhibits hybrid fracture?characteristics?of?dimples and extrusion flat caused by two crack surface peened each other. The fatigue striations were found only when Δεn/2 decreased to 0.4%.
2014, 43(6):1352-1356.
Abstract:
The dry sliding friction wear test of T6 treated Al-20Si-5Cu alloy was performed with UMT-2 tribometer. The wear mechanisms of the alloy were analyzed by means of SEM, EDS and OLS4000. The results reveal that the wear rate of Al-20Si-5Cu alloy is increased with the increase of applied load, but under high applied load, the wear rate is still small, showing a good wear resistance of the materials. The average friction coefficient changes within the range from 0.38 to 0.42, and the change is small over time, which indicates a strong stability. Meanwhile, as the applied load increases, the wear mechanism is changed from the oxidative wear and abrasive wear of low applied load to the fatigue wear.
The dry sliding friction wear test of T6 treated Al-20Si-5Cu alloy was performed with UMT-2 tribometer. The wear mechanisms of the alloy were analyzed by means of SEM, EDS and OLS4000. The results reveal that the wear rate of Al-20Si-5Cu alloy is increased with the increase of applied load, but under high applied load, the wear rate is still small, showing a good wear resistance of the materials. The average friction coefficient changes within the range from 0.38 to 0.42, and the change is small over time, which indicates a strong stability. Meanwhile, as the applied load increases, the wear mechanism is changed from the oxidative wear and abrasive wear of low applied load to the fatigue wear.
2014, 43(6):1372-1376.
Abstract:
The Nb3Sn superconducting strands used for ITER (international thermal-nuclear experimental reactor) consist of brittle intermetallic compounds. Due to the different coefficients of thermal expansion and different moduli of elasticity among the components, thermal strain is generated in the composite from heat treatment temperature down to room temperature, even to operating temperature (4.2 or 4.5 K). In order to research thermal strain and build the mathematic model of the Nb3Sn strands, local strain measurements during heating by means of quantum beams and tensile tests at room temperature were carried out. According to the elasto-plastic behavior of Nb3Sn revealed in the stress curves, the thermal strain was evaluated. The results show that the local strain exerted on superconducting (SC) filaments along the axial direction is compressive at room temperature and tensile at high temperatures. Moreover, the temperature dependence of thermal strain can be reproduced well by the numerical calculation method proposed in the paper.
The Nb3Sn superconducting strands used for ITER (international thermal-nuclear experimental reactor) consist of brittle intermetallic compounds. Due to the different coefficients of thermal expansion and different moduli of elasticity among the components, thermal strain is generated in the composite from heat treatment temperature down to room temperature, even to operating temperature (4.2 or 4.5 K). In order to research thermal strain and build the mathematic model of the Nb3Sn strands, local strain measurements during heating by means of quantum beams and tensile tests at room temperature were carried out. According to the elasto-plastic behavior of Nb3Sn revealed in the stress curves, the thermal strain was evaluated. The results show that the local strain exerted on superconducting (SC) filaments along the axial direction is compressive at room temperature and tensile at high temperatures. Moreover, the temperature dependence of thermal strain can be reproduced well by the numerical calculation method proposed in the paper.
2014, 43(6):1377-1380.
Abstract:
The thermodynamics and kinetics of natural rutile carbochlorination have been investigated in a fluidized-bed. Thermodynamic analysis of this system reveals that when C is excess in the solid phase, TiCl4 and CO are the only two stable products in the chemical equilibrium compositions system, and the increase of the ratio of C to TiO2 has little effect on the product composition. At high temperature, the reaction with CO as the product is the dominant reaction. This paper proposed a reaction rate model, and got a rutile chlorination rate formula, which is more consistent with experimental data. For the TiO2-C-Cl2 system, the reaction rate is dependent on both size and density of natural rutile. From 900 to 1000 oC, the apparent activation energy is 10.569 kJ/mol. In this temperature range, mass diffusion is the main reaction controlling step. The expression of the chlorine reaction rate in the C-Cl2 system was obtained, and it depends on the degree of reaction, Cl2 concentration and the size of coke.
The thermodynamics and kinetics of natural rutile carbochlorination have been investigated in a fluidized-bed. Thermodynamic analysis of this system reveals that when C is excess in the solid phase, TiCl4 and CO are the only two stable products in the chemical equilibrium compositions system, and the increase of the ratio of C to TiO2 has little effect on the product composition. At high temperature, the reaction with CO as the product is the dominant reaction. This paper proposed a reaction rate model, and got a rutile chlorination rate formula, which is more consistent with experimental data. For the TiO2-C-Cl2 system, the reaction rate is dependent on both size and density of natural rutile. From 900 to 1000 oC, the apparent activation energy is 10.569 kJ/mol. In this temperature range, mass diffusion is the main reaction controlling step. The expression of the chlorine reaction rate in the C-Cl2 system was obtained, and it depends on the degree of reaction, Cl2 concentration and the size of coke.
2014, 43(6):1381-1386.
Abstract:
5d transition metal Hf, Ta, W, Re and Ir is widely used in Ni-based single-crystal (SC) superalloys of the fourth and fifth generation, but for the mechanism, there is no theoretical and comprehensive research. Equilibrium lattice constant, formation enthalpy, cohesive energy, density of states, electron density difference and electronic populations of the pure and the 5d transition metals Hf, Ta, W, Re and Ir doped Ni3Al were studied by the plane-wave ultrasoft pseudopotential method based on the density functional theory. The calculations show that the occupational site of 5d transition metals Hf, Ta, W, R and Ir are of the Al site after doping; strongly orbital hybridization between the orbital electron of Ni 3d and Al 3p occur after Hf, Ta, W, Re, Ir doping, which lead to the bound electrons, smaller delocalization and narrower peak; Ni atoms and the first nearest neighbor Al atoms are covalent bonds in pure Ni3Al; however, Ni atoms and the first nearest neighbor X(Hf, Ta, W, Re, Ir) atoms are covalent bonds, which are gradually increased with the enlargement of atomic number of 5d transition metals.
5d transition metal Hf, Ta, W, Re and Ir is widely used in Ni-based single-crystal (SC) superalloys of the fourth and fifth generation, but for the mechanism, there is no theoretical and comprehensive research. Equilibrium lattice constant, formation enthalpy, cohesive energy, density of states, electron density difference and electronic populations of the pure and the 5d transition metals Hf, Ta, W, Re and Ir doped Ni3Al were studied by the plane-wave ultrasoft pseudopotential method based on the density functional theory. The calculations show that the occupational site of 5d transition metals Hf, Ta, W, R and Ir are of the Al site after doping; strongly orbital hybridization between the orbital electron of Ni 3d and Al 3p occur after Hf, Ta, W, Re, Ir doping, which lead to the bound electrons, smaller delocalization and narrower peak; Ni atoms and the first nearest neighbor Al atoms are covalent bonds in pure Ni3Al; however, Ni atoms and the first nearest neighbor X(Hf, Ta, W, Re, Ir) atoms are covalent bonds, which are gradually increased with the enlargement of atomic number of 5d transition metals.
16 First-Principles Calculations of Electronic Structure and Optical Properties of n-type Doped BaSnO3
2014, 43(6):1387-1391.
Abstract:
Based on density functional theory calculations, the stability, the electronic structure and optical properties of La and Nb doped BaSnO3 were investigated. The calculated results reveal that due to the electron doping, the Fermi level shifts into conduction bands and the system shows n-type degenerate semiconductor features. At the same time, the density of states (DOS) of the two systems shift towards low energies and the optical band gaps are broadened. The optical transmittance is higher than 80% in the visible range for La and Nb doped BaSnO3 systems.
Based on density functional theory calculations, the stability, the electronic structure and optical properties of La and Nb doped BaSnO3 were investigated. The calculated results reveal that due to the electron doping, the Fermi level shifts into conduction bands and the system shows n-type degenerate semiconductor features. At the same time, the density of states (DOS) of the two systems shift towards low energies and the optical band gaps are broadened. The optical transmittance is higher than 80% in the visible range for La and Nb doped BaSnO3 systems.
2014, 43(6):1392-1396.
Abstract:
A bioactive coating with no cracks was produced on the porous titanium by alkali-heat treatment. The morphology, element content and phase composition of the coating were analyzed by SEM, XRD and XPS. It is found that a micro-network structure mainly composed of bioactive sodium titanate and rutile covers the interior and exterior of porous titanium cells. And bioactive network without cracks is achievable with a given set of process parameters of the alkaline solution concentration and alkali-heat treatment time. After immersion into the SBF solution for 3 d, a carbonate-hydroxylapatite was detected by XRD on the cell surface of the porous titanium, showing a good compatibility of the porous titanium with bone.
A bioactive coating with no cracks was produced on the porous titanium by alkali-heat treatment. The morphology, element content and phase composition of the coating were analyzed by SEM, XRD and XPS. It is found that a micro-network structure mainly composed of bioactive sodium titanate and rutile covers the interior and exterior of porous titanium cells. And bioactive network without cracks is achievable with a given set of process parameters of the alkaline solution concentration and alkali-heat treatment time. After immersion into the SBF solution for 3 d, a carbonate-hydroxylapatite was detected by XRD on the cell surface of the porous titanium, showing a good compatibility of the porous titanium with bone.
2014, 43(6):1397-1402.
Abstract:
A chrome-free chemical conversion process using sodium stannate as the main component was investigated for corrosion protection of Mg-8.8Gd-3.1Y-0.6Zn-0.5Zr magnesium alloy (GW93). Corrosion property of the specimens with and without chemical conversion film was evaluated by full immersion test in neutral 3.5wt% NaCl solution. The microstructure and phase composition of the chemical conversion film were analyzed by optical microscope, X-ray diffraction meter and scanning electron microscope. The results show that the optimum chemical conversion processing for GW93 magnesium alloy is Na2SnO3 50 g/L, Na4P2O7 50 g/L, NaOH 5 g/L, CH3COONa 15 g/L, citric acid 3 g/L and sodium carbonate 20 g/L at 80 oC for 15 min. Mg-8.8Gd-3.1Y-0.6Zn-0.5Zr is covered by uniform chemical conversion coating composed of MgSnO3·3H2O. The immersion test shows that the average corrosion rate of the specimen without chemical conversion treatment is 6.1083 g·a-1·cm-2, and that of the specimens with chemical conversion treatment is 0.1264 g·a-1·cm-2. Corrosion resistance is improved by 97.9%, which suggests that stannate chemical conversion treatment could provide effective corrosion protection for GW93 magnesium alloy.
A chrome-free chemical conversion process using sodium stannate as the main component was investigated for corrosion protection of Mg-8.8Gd-3.1Y-0.6Zn-0.5Zr magnesium alloy (GW93). Corrosion property of the specimens with and without chemical conversion film was evaluated by full immersion test in neutral 3.5wt% NaCl solution. The microstructure and phase composition of the chemical conversion film were analyzed by optical microscope, X-ray diffraction meter and scanning electron microscope. The results show that the optimum chemical conversion processing for GW93 magnesium alloy is Na2SnO3 50 g/L, Na4P2O7 50 g/L, NaOH 5 g/L, CH3COONa 15 g/L, citric acid 3 g/L and sodium carbonate 20 g/L at 80 oC for 15 min. Mg-8.8Gd-3.1Y-0.6Zn-0.5Zr is covered by uniform chemical conversion coating composed of MgSnO3·3H2O. The immersion test shows that the average corrosion rate of the specimen without chemical conversion treatment is 6.1083 g·a-1·cm-2, and that of the specimens with chemical conversion treatment is 0.1264 g·a-1·cm-2. Corrosion resistance is improved by 97.9%, which suggests that stannate chemical conversion treatment could provide effective corrosion protection for GW93 magnesium alloy.
2014, 43(6):1403-1406.
Abstract:
Using high purity W-Si alloy powder (> 99.995%) as raw material, high purity W-Si alloy target was prepared by vacuum hot pressing sintering process. The effects of process parameters, including sintering temperature, hot pressing pressure and holding time, on the target performance of density and microstructure were investigated. The results show that under the process parameters of sintering temperature of 1350~1380 oC, hot pressing pressure of 25~30 MPa, and holding time of 1.5~2 h, high performance W-Si alloy target could be prepared with more than 99% relative density and average grain size less than 100 μm.
Using high purity W-Si alloy powder (> 99.995%) as raw material, high purity W-Si alloy target was prepared by vacuum hot pressing sintering process. The effects of process parameters, including sintering temperature, hot pressing pressure and holding time, on the target performance of density and microstructure were investigated. The results show that under the process parameters of sintering temperature of 1350~1380 oC, hot pressing pressure of 25~30 MPa, and holding time of 1.5~2 h, high performance W-Si alloy target could be prepared with more than 99% relative density and average grain size less than 100 μm.
2014, 43(6):1407-1411.
Abstract:
A NiCrAlY/Al duplex coating was prepared by arc ion plating and magnetron sputtering. The effects of the duplex coating on oxidation at elevated temperature were investigated. After exposure in air at 950 oC for 100 h, the mass gain of the NiCrAlY/Al coated specimen is much smaller than that of the uncoated substrate, and no peeling is found in the NiCrAlY/Al coating. SEM, EDS and XRD have been used to study the microstructure, elements distribution vs. depth and phase formation of the two oxidized layers. Due to the loose structure, the scale on the bare substrate could not contribute a reliable protection against intrusive oxygen at high temperature. As an oxygen barrier, the NiCrAlY/Al coating is capable of forming a protective scale which is consisted of Cr2O3, α-Al2O3 and β-NiAl. The Al interlayer plays a role of aluminizing resource for the formation of protective Al2O3 layer. All the results indicate that the oxidation resistance of γ-TiAl alloy has been improved effectively by NiCrAlY/Al duplex coating.
A NiCrAlY/Al duplex coating was prepared by arc ion plating and magnetron sputtering. The effects of the duplex coating on oxidation at elevated temperature were investigated. After exposure in air at 950 oC for 100 h, the mass gain of the NiCrAlY/Al coated specimen is much smaller than that of the uncoated substrate, and no peeling is found in the NiCrAlY/Al coating. SEM, EDS and XRD have been used to study the microstructure, elements distribution vs. depth and phase formation of the two oxidized layers. Due to the loose structure, the scale on the bare substrate could not contribute a reliable protection against intrusive oxygen at high temperature. As an oxygen barrier, the NiCrAlY/Al coating is capable of forming a protective scale which is consisted of Cr2O3, α-Al2O3 and β-NiAl. The Al interlayer plays a role of aluminizing resource for the formation of protective Al2O3 layer. All the results indicate that the oxidation resistance of γ-TiAl alloy has been improved effectively by NiCrAlY/Al duplex coating.
2014, 43(6):1412-1416.
Abstract:
A series of TaMoN composite films with different Mo contents were fabricated by a magnetron sputtering technique. The microstructures, morphology, phase composition, mechanical and friction properties of the films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and equipped EDS, nano-indentation, and CSM high-temperature ball-on-disc tribo-meter. The results show that the microstructure of TaMoN composite films is a poly-phase structure consisting of cubic, hexagonal and orthorhombic structure by adding Mo element to TaN film. The hardness of TaMoN composite film is higher than that of TaN monolayer film due to the solid solution strengthening. The friction coefficients of TaMoN films at room and high temperatures are lower than that of TaN film, and the reasons were analyzed based on the morphology and wear tracks formed at different temperatures.
A series of TaMoN composite films with different Mo contents were fabricated by a magnetron sputtering technique. The microstructures, morphology, phase composition, mechanical and friction properties of the films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and equipped EDS, nano-indentation, and CSM high-temperature ball-on-disc tribo-meter. The results show that the microstructure of TaMoN composite films is a poly-phase structure consisting of cubic, hexagonal and orthorhombic structure by adding Mo element to TaN film. The hardness of TaMoN composite film is higher than that of TaN monolayer film due to the solid solution strengthening. The friction coefficients of TaMoN films at room and high temperatures are lower than that of TaN film, and the reasons were analyzed based on the morphology and wear tracks formed at different temperatures.
2014, 43(6):1417-1422.
Abstract:
The surfaces of maghemite nanoparticles prepared from magnetite by calcination process, were modified by 3-triethoxysilylpropylamine (APTES). The chloroplatinic acid/palladium chloride was added into APTES-maghemite NPs solution, and accordingly, the Pt4+/Pd2+ was absorbed on the surface and formed a coordinated compound with amino groups. Finally, the complexed Pt4+/Pd2+ was reduced by hydrazine hydrate (HHA) to generate magnetic γ-Fe2O3/M (M=Pt/Pd) nanocomposites under ultrasonic application. The morphology, microstructure, composition and magnetic properties of the γ-Fe2O3/M NPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM) and superconducting quantum interference device (SQUID) magnetometry. The results show that the diameters of precursor maghemite nanoparticles are about 20 nm, and those of the γ-Fe2O3/Pt and γ-Fe2O3/Pd nanoparticles are about 68 and 36 nm, respectively. Their magnetic performances have shown a saturation magnetization (Ms) of about 29.4 and 31.2 (A·m2)/kg at room temperature, respectively. The superior magnetic response property for magnetic sensitive catalyst system will be further investigated. These kinds of nanoparticles have provided a new way for recovering of Pt and Pd catalyzer and application of magnetosensitive catalyst system.
The surfaces of maghemite nanoparticles prepared from magnetite by calcination process, were modified by 3-triethoxysilylpropylamine (APTES). The chloroplatinic acid/palladium chloride was added into APTES-maghemite NPs solution, and accordingly, the Pt4+/Pd2+ was absorbed on the surface and formed a coordinated compound with amino groups. Finally, the complexed Pt4+/Pd2+ was reduced by hydrazine hydrate (HHA) to generate magnetic γ-Fe2O3/M (M=Pt/Pd) nanocomposites under ultrasonic application. The morphology, microstructure, composition and magnetic properties of the γ-Fe2O3/M NPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM) and superconducting quantum interference device (SQUID) magnetometry. The results show that the diameters of precursor maghemite nanoparticles are about 20 nm, and those of the γ-Fe2O3/Pt and γ-Fe2O3/Pd nanoparticles are about 68 and 36 nm, respectively. Their magnetic performances have shown a saturation magnetization (Ms) of about 29.4 and 31.2 (A·m2)/kg at room temperature, respectively. The superior magnetic response property for magnetic sensitive catalyst system will be further investigated. These kinds of nanoparticles have provided a new way for recovering of Pt and Pd catalyzer and application of magnetosensitive catalyst system.
2014, 43(6):1427-1431.
Abstract:
The effects of combined C2Cl6 degasser and ultrasonic treatment on the hydrogen content in the Al-3.06%Si, Al-3.21%Mg and 2024 aluminum alloys and the mechanical properties of 2024 aluminum alloy were studied. The results show that the degassing time with a single ultrasonic treatment is greatly shortened by the combined treatment. Furthermore, the mechanical properties of the 2024 alloy are also significantly affected by the combined treatment: the tensile strength and elongation are increased by 28.3% and 92.3% (maximum increase), respectively, compared with those without any treatment. However, the yield strength is slightly affected by the degassing treatment (with an increase of only 6.7%, maximum increase). In addition, with the degassing treatment, the fracture mode is transformed from brittle fracture to microvoid coalescence fracture, improving the mechanical properties of the alloy.
The effects of combined C2Cl6 degasser and ultrasonic treatment on the hydrogen content in the Al-3.06%Si, Al-3.21%Mg and 2024 aluminum alloys and the mechanical properties of 2024 aluminum alloy were studied. The results show that the degassing time with a single ultrasonic treatment is greatly shortened by the combined treatment. Furthermore, the mechanical properties of the 2024 alloy are also significantly affected by the combined treatment: the tensile strength and elongation are increased by 28.3% and 92.3% (maximum increase), respectively, compared with those without any treatment. However, the yield strength is slightly affected by the degassing treatment (with an increase of only 6.7%, maximum increase). In addition, with the degassing treatment, the fracture mode is transformed from brittle fracture to microvoid coalescence fracture, improving the mechanical properties of the alloy.
2014, 43(6):1441-1446.
Abstract:
The effects of rolling temperature, deformation degree and heat treatment on the microstructure of Ti-1300 alloy were studied with an emphasis on the relationship between the heat processing technique and microscopic structure. The results show that Ti-1300 alloy with rolling temperature under β-transus temperature is composed of spherical α phase and equiaxed β phase, and α phase dissolves into β matrix with increasing of the rolling temperature. When the rolling temperature is increased to β-transus temperature or higher, the equiaxed β phase becomes the only dominant phase. The grains of Ti-1300 alloy with large deformation can be greatly refined, and the structure becomes homogeneous. After α+β phase region solution treatment, α phase with sphericity or strip shape precipitate in grain boundary and intergranular position and then disperse in metastable β matrix, and lead to dispersion strengthening and fine grain strengthening; however, the alloy after β phase region solution treatment is mainly composed of equiaxed β phase with the average grain size of about 60 μm. The Ti-1300 alloy after aging treatment is composed of strip αp phase, acicular αs phase and β matrix. There is few influence of the heat processing technique on the morphology parameters of αp phase in Ti-1300 alloy after aging treatment, but the morphology of αp and αs phase grow up with the aging temperature increasing. Acicular αs phase is dispersed on the β matrix.
The effects of rolling temperature, deformation degree and heat treatment on the microstructure of Ti-1300 alloy were studied with an emphasis on the relationship between the heat processing technique and microscopic structure. The results show that Ti-1300 alloy with rolling temperature under β-transus temperature is composed of spherical α phase and equiaxed β phase, and α phase dissolves into β matrix with increasing of the rolling temperature. When the rolling temperature is increased to β-transus temperature or higher, the equiaxed β phase becomes the only dominant phase. The grains of Ti-1300 alloy with large deformation can be greatly refined, and the structure becomes homogeneous. After α+β phase region solution treatment, α phase with sphericity or strip shape precipitate in grain boundary and intergranular position and then disperse in metastable β matrix, and lead to dispersion strengthening and fine grain strengthening; however, the alloy after β phase region solution treatment is mainly composed of equiaxed β phase with the average grain size of about 60 μm. The Ti-1300 alloy after aging treatment is composed of strip αp phase, acicular αs phase and β matrix. There is few influence of the heat processing technique on the morphology parameters of αp phase in Ti-1300 alloy after aging treatment, but the morphology of αp and αs phase grow up with the aging temperature increasing. Acicular αs phase is dispersed on the β matrix.
2014, 43(6):1447-1451.
Abstract:
The inhibition effect of sodium chromate (Na2CrO4) on uranium-titanium (U-Ti) alloy in 200 mg/L NaCl solution was evaluated with the weight-loss method and the electrochemical method. The feature of the oxide film formed on the U-Ti alloy sample surface was analyzed with X-ray photoelectron spectroscopy (XPS) and laser confocal microscope. The results show that Na2CrO4 is anodic inhibitor for U-Ti alloy and the inhibition efficiency increases with its concentration increasing. The efficiency is influenced greatly by the temperature of corrosion solution. The corrosion rate of U-Ti alloy sample is greater in 100 mg/L Na2CrO4 solution than in uninhibited solution when the solution temperature is higher than 45 oC. The XPS analysis indicates that there are two types of uranium oxide in the passive film of U-Ti alloy surface. UO2+x is in the outer layer in the film while UO2 in the inner layer. The outer layer of passive film includes UO2+x and some chromium compounds when Na2CrO4 is added into NaCl solution, and the thickness of the outer layer is less than 3 nm.
The inhibition effect of sodium chromate (Na2CrO4) on uranium-titanium (U-Ti) alloy in 200 mg/L NaCl solution was evaluated with the weight-loss method and the electrochemical method. The feature of the oxide film formed on the U-Ti alloy sample surface was analyzed with X-ray photoelectron spectroscopy (XPS) and laser confocal microscope. The results show that Na2CrO4 is anodic inhibitor for U-Ti alloy and the inhibition efficiency increases with its concentration increasing. The efficiency is influenced greatly by the temperature of corrosion solution. The corrosion rate of U-Ti alloy sample is greater in 100 mg/L Na2CrO4 solution than in uninhibited solution when the solution temperature is higher than 45 oC. The XPS analysis indicates that there are two types of uranium oxide in the passive film of U-Ti alloy surface. UO2+x is in the outer layer in the film while UO2 in the inner layer. The outer layer of passive film includes UO2+x and some chromium compounds when Na2CrO4 is added into NaCl solution, and the thickness of the outer layer is less than 3 nm.
2014, 43(6):1457-1461.
Abstract:
Fine ammonium paratungstate was prepared by microwave-ultrasonic cooperative evaporation crystallization without external force or any surfactant. The effects of temperature, ammonium tungstate concentration, power of microwave and ultrasonic, as well as cooperative time on the particle size and morphology of ammonium paratungstate were investigated. Under the optimum conditions, the fine single-crystal ammonium paratungstate with an average particle size of 7.6 μm, uniform size distribution, perfect crystal, and five crystal water could be prepared.
Fine ammonium paratungstate was prepared by microwave-ultrasonic cooperative evaporation crystallization without external force or any surfactant. The effects of temperature, ammonium tungstate concentration, power of microwave and ultrasonic, as well as cooperative time on the particle size and morphology of ammonium paratungstate were investigated. Under the optimum conditions, the fine single-crystal ammonium paratungstate with an average particle size of 7.6 μm, uniform size distribution, perfect crystal, and five crystal water could be prepared.
2014, 43(6):1462-1466.
Abstract:
Using Pd(en)2Cl2 as the Pd precursor and graphite oxide as the carbon precursor, the Pd(en)22+ intercalated graphite oxide was synthesized, then it was reduced in solution with NaBH4 and the graphene/Pd nanosized particle composites were obtained. The final graphene composites were characterized by XRD, FE-SEM, TEM, ICP and N2 adsorption test and their H2 storage property was also measured. The results show that the composites have a regular mesoporous structure, and Pd particles with a diameter of 2~6 nm are evenly dispersed between graphene sheets and pillar the graphene sheets to inhibit the accumulation of grapheme sheets. The composites have a high BET surface area and their H2 storage reaches 3.4 wt% at 77 K and 0.11 MPa.
Using Pd(en)2Cl2 as the Pd precursor and graphite oxide as the carbon precursor, the Pd(en)22+ intercalated graphite oxide was synthesized, then it was reduced in solution with NaBH4 and the graphene/Pd nanosized particle composites were obtained. The final graphene composites were characterized by XRD, FE-SEM, TEM, ICP and N2 adsorption test and their H2 storage property was also measured. The results show that the composites have a regular mesoporous structure, and Pd particles with a diameter of 2~6 nm are evenly dispersed between graphene sheets and pillar the graphene sheets to inhibit the accumulation of grapheme sheets. The composites have a high BET surface area and their H2 storage reaches 3.4 wt% at 77 K and 0.11 MPa.
2014, 43(6):1467-1472.
Abstract:
The intergranular corrosion behavior, exfoliation corrosion behavior, stress corrosion behavior and microstructures of 2099 Al-Li alloy in different aging conditions were investigated by OM, TEM and slow strain rate tensile testing. The results show that the corrosion resistance of the alloy is improved with aging time. In the under-aged condition, the remained AlCuFeMn phases at grain boundaries result in low corrosion resistance of the under-aged alloy. In the peak-aged condition, many T1 phases precipitate in the matrix, promoting the incensement of corrosion resistance of the alloy. In the over-aged condition, a great number of T1 phases still remain the morphology as that in the peak-aged alloy, and the coarse precipitates distribute along the grain boundaries with large space inducing the further growth of corrosion resistance of the alloy.
The intergranular corrosion behavior, exfoliation corrosion behavior, stress corrosion behavior and microstructures of 2099 Al-Li alloy in different aging conditions were investigated by OM, TEM and slow strain rate tensile testing. The results show that the corrosion resistance of the alloy is improved with aging time. In the under-aged condition, the remained AlCuFeMn phases at grain boundaries result in low corrosion resistance of the under-aged alloy. In the peak-aged condition, many T1 phases precipitate in the matrix, promoting the incensement of corrosion resistance of the alloy. In the over-aged condition, a great number of T1 phases still remain the morphology as that in the peak-aged alloy, and the coarse precipitates distribute along the grain boundaries with large space inducing the further growth of corrosion resistance of the alloy.
2014, 43(6):1473-1478.
Abstract:
The effect of Immunoglobulin G (IgG) and Sodium Hyaluronat (HA) on the corrosion behavior of TZNT alloy, as a type of potential artificial joint materials, has been investigated in PBS solution (pH=7.4) through electrochemical tests. The results show that the growth of the surface oxide film on TZNT alloy in PBS can be inhibited by the addition of IgG to some extent. HA is effective to decrease the corrosion rate of TZNT alloy, and it is influenced by the concentration and immersion period, and the best inhibitive effect can be obtained when the samples is exposed in test solution including 2.5 g/L HA after 72 h immersion.
The effect of Immunoglobulin G (IgG) and Sodium Hyaluronat (HA) on the corrosion behavior of TZNT alloy, as a type of potential artificial joint materials, has been investigated in PBS solution (pH=7.4) through electrochemical tests. The results show that the growth of the surface oxide film on TZNT alloy in PBS can be inhibited by the addition of IgG to some extent. HA is effective to decrease the corrosion rate of TZNT alloy, and it is influenced by the concentration and immersion period, and the best inhibitive effect can be obtained when the samples is exposed in test solution including 2.5 g/L HA after 72 h immersion.
2014, 43(6):1483-1486.
Abstract:
Ni-P-(nano)TiO2 composite coating was prepared by electroless composite plating. The effects of nano-TiO2 addition on microstructure, hardness, wear resistance, porosity and corrosion resistance of Ni-P composite coating were investigated and the mechanism was discussed. The results show that TiO2 nanoparticles are homogeneously distributed in the Ni based coatings, without apparent aggregation. The dispersion strengthening effect of the nano-TiO2 particles leads to high hardness and good wear resistance of the composite coating. The surface hardness of the crystallized composite coating can reach 10925 MPa and the wear resistance increases greatly. However, nano-TiO2 particles addition increases the porosity of the coating, decreases the corrosion resistance to NaOH and NaCl solution slightly, and the corrosion resistance to HCl becomes poor.
Ni-P-(nano)TiO2 composite coating was prepared by electroless composite plating. The effects of nano-TiO2 addition on microstructure, hardness, wear resistance, porosity and corrosion resistance of Ni-P composite coating were investigated and the mechanism was discussed. The results show that TiO2 nanoparticles are homogeneously distributed in the Ni based coatings, without apparent aggregation. The dispersion strengthening effect of the nano-TiO2 particles leads to high hardness and good wear resistance of the composite coating. The surface hardness of the crystallized composite coating can reach 10925 MPa and the wear resistance increases greatly. However, nano-TiO2 particles addition increases the porosity of the coating, decreases the corrosion resistance to NaOH and NaCl solution slightly, and the corrosion resistance to HCl becomes poor.
2014, 43(6):1487-1491.
Abstract:
A novel method, ultra-frequency induction heating and hydrothermal treatment composite method, was applied to load hydroxyapatite (HA) onto porous titanium substrate. The composition, microstructure, and morphology of as-achieved HA were characterized by XRF, XRD, FTIR and SEM. The adsorption ability of Pb2+, Cr2+ and Ni2+ was measured by ICP. The results show that HA possesses lots of carbonate groups in its lattice, and the absorption of Pb2+, Cr2+ and Ni2+ could reach 97.5%, 97.3% and 97.6%, respectively.
A novel method, ultra-frequency induction heating and hydrothermal treatment composite method, was applied to load hydroxyapatite (HA) onto porous titanium substrate. The composition, microstructure, and morphology of as-achieved HA were characterized by XRF, XRD, FTIR and SEM. The adsorption ability of Pb2+, Cr2+ and Ni2+ was measured by ICP. The results show that HA possesses lots of carbonate groups in its lattice, and the absorption of Pb2+, Cr2+ and Ni2+ could reach 97.5%, 97.3% and 97.6%, respectively.
2014, 43(6):1492-1496.
Abstract:
Superplastic mechanical behavior of Ti-48Al-2.3Cr-0.2Mo (at%) alloy with deformed microstructure was investigated at temperatures ranging from 800 to 1100 oC with strain rates between 5′10-5 and 1′10-3 s-1 by constant strain rate tests and incremental strain rate tests. Depending on the plots of true stress-true strain and the data of activation energy calculated in the tests, the mechanism of superplasticity was discussed. Results show that for the Ti-48Al-2.3Cr-0.2Mo alloy, there is almost no constant stress stage but hardening is observed in the plots of true stress-true strain. Particularly, at the temperatures above 1025 oC or strain rates below 5′10-4 s-1, a continuous strain hardening stage is observed, and with the increasing of the temperature and the decreasing of the strain rate, the stage increases. High-density dislocation caused by pre-deformation is suggested the reason of hardening. At temperatures from 800 to 900oC, the maximum strain rate sensitivity (m) values are 0.52~0.67, and the activation energy of the alloy is calculated as Qapp =178 kJ/mol, indicating that the dominant mechanism of superplastic deformation is grain boundary siding controlled by grain boundary diffusion. At temperatures from 950 to 1100 oC, the maximum strain rate sensitivity (m) values are 0.63~0.77, and the activation energy of the alloy is calculated as Qapp =290 kJ/mol, suggesting that the dominant mechanism of superplastic deformation is grain boundary siding controlled by lattice diffusion.
Superplastic mechanical behavior of Ti-48Al-2.3Cr-0.2Mo (at%) alloy with deformed microstructure was investigated at temperatures ranging from 800 to 1100 oC with strain rates between 5′10-5 and 1′10-3 s-1 by constant strain rate tests and incremental strain rate tests. Depending on the plots of true stress-true strain and the data of activation energy calculated in the tests, the mechanism of superplasticity was discussed. Results show that for the Ti-48Al-2.3Cr-0.2Mo alloy, there is almost no constant stress stage but hardening is observed in the plots of true stress-true strain. Particularly, at the temperatures above 1025 oC or strain rates below 5′10-4 s-1, a continuous strain hardening stage is observed, and with the increasing of the temperature and the decreasing of the strain rate, the stage increases. High-density dislocation caused by pre-deformation is suggested the reason of hardening. At temperatures from 800 to 900oC, the maximum strain rate sensitivity (m) values are 0.52~0.67, and the activation energy of the alloy is calculated as Qapp =178 kJ/mol, indicating that the dominant mechanism of superplastic deformation is grain boundary siding controlled by grain boundary diffusion. At temperatures from 950 to 1100 oC, the maximum strain rate sensitivity (m) values are 0.63~0.77, and the activation energy of the alloy is calculated as Qapp =290 kJ/mol, suggesting that the dominant mechanism of superplastic deformation is grain boundary siding controlled by lattice diffusion.
2014, 43(6):1497-1501.
Abstract:
Using ascorbic acid as a reducing agent, AgNO3 as silver salts and polyethylene glycol 4000(PEG-4000) as dispersant, sub-micron spherical silver powders were prepared by a liquid-phase reduction method. By means of the orthogonal design of three factors and three levels, the effects of the following factors on the particles size of silver powders were studied, including the concentration of ascorbic acid, the way of dispersant addition into solution and the pH value of the solution. The optimized preparation conditions of sub-micron spherical silver powders were obtained. The sub-micron spherical silver powders could be synthesized under the conditions of pH=5, AgNO3 concentration of 0.5 mol/L, adding half of the dispersant to the AgNO3 and ascorbic acid solution, C6H8O6 concentration of 0.9 mol/L, PEG-4000/AgNO3 mass ratio of 1.2 and at room temperature. The sub-micron spherical silver powders were characterized by laser particle distribution analyzer, SEM and XRD.The results show that the prepared silver powders are pure, with uniform particle size distribution and spherical shape under optimized experiment conditions. The paste prepared with the obtained silver powders was printed on the silicon, and the square resistance of the sintered film is 0.721 mΩ/□, indicating the electrical property of the prepared silver is qualified for solar cells.
Using ascorbic acid as a reducing agent, AgNO3 as silver salts and polyethylene glycol 4000(PEG-4000) as dispersant, sub-micron spherical silver powders were prepared by a liquid-phase reduction method. By means of the orthogonal design of three factors and three levels, the effects of the following factors on the particles size of silver powders were studied, including the concentration of ascorbic acid, the way of dispersant addition into solution and the pH value of the solution. The optimized preparation conditions of sub-micron spherical silver powders were obtained. The sub-micron spherical silver powders could be synthesized under the conditions of pH=5, AgNO3 concentration of 0.5 mol/L, adding half of the dispersant to the AgNO3 and ascorbic acid solution, C6H8O6 concentration of 0.9 mol/L, PEG-4000/AgNO3 mass ratio of 1.2 and at room temperature. The sub-micron spherical silver powders were characterized by laser particle distribution analyzer, SEM and XRD.The results show that the prepared silver powders are pure, with uniform particle size distribution and spherical shape under optimized experiment conditions. The paste prepared with the obtained silver powders was printed on the silicon, and the square resistance of the sintered film is 0.721 mΩ/□, indicating the electrical property of the prepared silver is qualified for solar cells.
2014, 43(6):1507-1510.
Abstract:
The microstructure and mechanical properties of Ti-5553 alloy bars with large diameter Φ300 mm were investigated. The result indicates that the influence of the solution temperature changes on mechanical properties is remarkable. When the Ti-5553 alloy is subjected to BASCA heat treatment, it reveals high damage-tolerant property including the fracture toughness up to 87.3 MPa·m1/2 and the strength up to 1100 MPa. After solution treatment at 820 oC and aging treatment from 580 to 620 oC, a large amount of primary equiaxial a phases and secondary acicular a phases distribute in the β matrix.?The mechanical properties of Ti-5553 alloy are determined by the relative volume fraction of primary a and secondary a phases.
The microstructure and mechanical properties of Ti-5553 alloy bars with large diameter Φ300 mm were investigated. The result indicates that the influence of the solution temperature changes on mechanical properties is remarkable. When the Ti-5553 alloy is subjected to BASCA heat treatment, it reveals high damage-tolerant property including the fracture toughness up to 87.3 MPa·m1/2 and the strength up to 1100 MPa. After solution treatment at 820 oC and aging treatment from 580 to 620 oC, a large amount of primary equiaxial a phases and secondary acicular a phases distribute in the β matrix.?The mechanical properties of Ti-5553 alloy are determined by the relative volume fraction of primary a and secondary a phases.
2014, 43(6):1518-1524.
Abstract:
The research and application progress of Ti alloy oil country tubular goods (OCTGs) at home and abroad were reviewed, and the chemical composition, microstructure and mechanical properties of Ti alloy OCTGs were also referred. The resistance to uniform corrosion, local corrosion, erosion, corrosion fatigue and stress corrosion cracking (SCC) of Ti alloy OCTGs in the environments of the completion fluid, the acidizing fluid and the production conditions were discussed. Moreover, the gap in the research and development of the Ti alloy OCTGs between China and foreign countries was pointed out, and the application prospect and the development trend of Ti alloy OCTGs in the well of high pressure and high temperature (HPHT) oil and gas field were also forecasted.
The research and application progress of Ti alloy oil country tubular goods (OCTGs) at home and abroad were reviewed, and the chemical composition, microstructure and mechanical properties of Ti alloy OCTGs were also referred. The resistance to uniform corrosion, local corrosion, erosion, corrosion fatigue and stress corrosion cracking (SCC) of Ti alloy OCTGs in the environments of the completion fluid, the acidizing fluid and the production conditions were discussed. Moreover, the gap in the research and development of the Ti alloy OCTGs between China and foreign countries was pointed out, and the application prospect and the development trend of Ti alloy OCTGs in the well of high pressure and high temperature (HPHT) oil and gas field were also forecasted.
2014, 43(6):1525-1530.
Abstract:
This paper reviews the new progress of studies of lithium-air batteries. The charge and discharge mechanism, air electrode, and electrolyte are discussed. In addition, the future direction of development of the lithium-air battery field is prospected.
This paper reviews the new progress of studies of lithium-air batteries. The charge and discharge mechanism, air electrode, and electrolyte are discussed. In addition, the future direction of development of the lithium-air battery field is prospected.
2014, 43(6):1531-1536.
Abstract:
The common preparation methods of L10-FePt nanoparticles have been reviewed. The development of typical experiment synthesis methods of the nanoparticles for reducing the phase transition temperature has been summarized. Additionally, the latest research progress in structure, magnetic property and self-assembly of L10-FePt nanoparticles has been discussed.
The common preparation methods of L10-FePt nanoparticles have been reviewed. The development of typical experiment synthesis methods of the nanoparticles for reducing the phase transition temperature has been summarized. Additionally, the latest research progress in structure, magnetic property and self-assembly of L10-FePt nanoparticles has been discussed.
Hu Ping
,
Wang Kuaishe
,
Yang Fan
,
He Huancheng
,
Kang Xuanqi
,
Wang Hua
,
Yu Zhitao
,
Tan Jiangfei
2014, 43(6):1502-1506.
Abstract:
Using the stearic acid as carbon source to replace graphite, TZM alloy was doped with carbon by a solid-liquid mixing method. The TZM sheet was prepared by hot-rolling, warm-rolling, cold rolling and other techniques. The mechanical properties and metallographic structure of the TZM sheet were analyzed. The results show that the TZM alloy powder is mixed more evenly using stearic acid as carbon source than using graphite as carbon source. The second phase is more and smaller. The second phase particles take a pinning effect on the dislocation, hinder the slip of the grain boundaries, and thus increase the tensile strength of TZM alloy, which is 1168 MPa and improved by 15.3%, and the elongation is 7.66%.
Using the stearic acid as carbon source to replace graphite, TZM alloy was doped with carbon by a solid-liquid mixing method. The TZM sheet was prepared by hot-rolling, warm-rolling, cold rolling and other techniques. The mechanical properties and metallographic structure of the TZM sheet were analyzed. The results show that the TZM alloy powder is mixed more evenly using stearic acid as carbon source than using graphite as carbon source. The second phase is more and smaller. The second phase particles take a pinning effect on the dislocation, hinder the slip of the grain boundaries, and thus increase the tensile strength of TZM alloy, which is 1168 MPa and improved by 15.3%, and the elongation is 7.66%.
