Volume 40,Issue 9,2011 Table of Contents
2011, 40(9):1505-1509.
Abstract:
The canned forging pancake of Ti-45Al-5.4V-3.6Nb-0.3Y alloy was prepared, and the microstructure control and properties for various microstructures of as-forged alloy were studied. Three different microstructures, duplex, nearly lamellar and fully lamellar, were obtained through heat treatments. The microstructure evolution was analyzed and tensile properties were measured. The results show that the treated sample with duplex microstructure exhibits the best ductility, and its elongation reaches 1.35%; the alloy with nearly lamellar microstructure has better strength, i.e.yield strength and fracture strength are 605.31 MPa and 665.75 MPa at room temperature, respectively
The canned forging pancake of Ti-45Al-5.4V-3.6Nb-0.3Y alloy was prepared, and the microstructure control and properties for various microstructures of as-forged alloy were studied. Three different microstructures, duplex, nearly lamellar and fully lamellar, were obtained through heat treatments. The microstructure evolution was analyzed and tensile properties were measured. The results show that the treated sample with duplex microstructure exhibits the best ductility, and its elongation reaches 1.35%; the alloy with nearly lamellar microstructure has better strength, i.e.yield strength and fracture strength are 605.31 MPa and 665.75 MPa at room temperature, respectively
2011, 40(9):1510-1513.
Abstract:
We reported the fabrication of self-organized, vertically oriented Ti-Fe-O nanotube array films grown by anodization of Ti-xFe alloys in an ethylene glycol and NH4F mixed electrolyte and their Uv-Vis spectrum (200-1000 nm) photoresponse properties. The key factor affecting the morphology is the Fe content. The higher the Fe content is, the flatter the nanotubes surface is, and the more disorder the bottom surface appears. XRD and photoresponse measurements demonstrate the realizable iron doping of the nanotube layers, which leads to a significant visible photoresponse. The Ti-12Fe sample prepared has a high photoresponse in visible range of the spectrum
We reported the fabrication of self-organized, vertically oriented Ti-Fe-O nanotube array films grown by anodization of Ti-xFe alloys in an ethylene glycol and NH4F mixed electrolyte and their Uv-Vis spectrum (200-1000 nm) photoresponse properties. The key factor affecting the morphology is the Fe content. The higher the Fe content is, the flatter the nanotubes surface is, and the more disorder the bottom surface appears. XRD and photoresponse measurements demonstrate the realizable iron doping of the nanotube layers, which leads to a significant visible photoresponse. The Ti-12Fe sample prepared has a high photoresponse in visible range of the spectrum
2011, 40(9):1514-1518.
Abstract:
The hydrogen absorption kinetics of Ti40 alloy was studied in the temperature range of 550-700 °C and the pressure range of 15.88-45.88 kPa. The initial temperature of hydrogen absorption for Ti40 alloy is 515 °C. With the increase of temperature and initial hydrogen pressure, the time to reach the equilibrium condition becomes shorter, while hydrogen absorption rate and equilibrium hydrogen pressure increase. At low temperature, the process of hydrogen absorption consists of three stages: Ⅰincubation stage, Ⅱ the first absorption stage and Ⅲ the second absorption stage. At the same temperature, the rate constants at different stages follow the relation: kⅡ＞kⅠ＞kⅢ. At the same stage, the rate constants increase with the increase of temperature. The activation energy of the first and second absorption stage are 73.3 kJ/mol and 29.6 kJ/mol, respectively. The rate controlling step at the second absorption stage is the hydrogen diffusion in β-Ti
The hydrogen absorption kinetics of Ti40 alloy was studied in the temperature range of 550-700 °C and the pressure range of 15.88-45.88 kPa. The initial temperature of hydrogen absorption for Ti40 alloy is 515 °C. With the increase of temperature and initial hydrogen pressure, the time to reach the equilibrium condition becomes shorter, while hydrogen absorption rate and equilibrium hydrogen pressure increase. At low temperature, the process of hydrogen absorption consists of three stages: Ⅰincubation stage, Ⅱ the first absorption stage and Ⅲ the second absorption stage. At the same temperature, the rate constants at different stages follow the relation: kⅡ＞kⅠ＞kⅢ. At the same stage, the rate constants increase with the increase of temperature. The activation energy of the first and second absorption stage are 73.3 kJ/mol and 29.6 kJ/mol, respectively. The rate controlling step at the second absorption stage is the hydrogen diffusion in β-Ti
2011, 40(9):1519-1521.
Abstract:
The cyclic stability and the high-rate discharge characteristic of Ti0.17Zr0.08V0.35Cr0.1Ni0.3 alloy at 333 K were investigated. The results show that the discharge capacity of Ti0.17Zr0.08V0.35Cr0.1Ni0.3 alloy is ~450 mAh/g at a current density of 60 mA/g at 333 K for the first cycle, and then it obviously decreases with increasing of cycle number. It should be noted that the excellent discharge capacity of Ti0.17Zr0.08V0.35Cr0.1Ni0.3 alloy will remain 160 mAh/g at a current density of 2400 mA/g to cut-off voltage of 0.6 V. Moreover, the possible factors affecting the electrochemical performance of this alloy were discussed
The cyclic stability and the high-rate discharge characteristic of Ti0.17Zr0.08V0.35Cr0.1Ni0.3 alloy at 333 K were investigated. The results show that the discharge capacity of Ti0.17Zr0.08V0.35Cr0.1Ni0.3 alloy is ~450 mAh/g at a current density of 60 mA/g at 333 K for the first cycle, and then it obviously decreases with increasing of cycle number. It should be noted that the excellent discharge capacity of Ti0.17Zr0.08V0.35Cr0.1Ni0.3 alloy will remain 160 mAh/g at a current density of 2400 mA/g to cut-off voltage of 0.6 V. Moreover, the possible factors affecting the electrochemical performance of this alloy were discussed
2011, 40(9):1522-1525.
Abstract:
The morphology evolution and creep behavior of g ￠ phase in [001] and [011] oriented specimens of a nickel-base single crystal superalloy during the tensile creep at 1253 K and 200 MPa were investigated. SEM and TEM observation shows that the direction coarsening of precipitates is highly dependent on the crystal orientation. In [001] orientation, the g ￠ phase transits from original cuboids to the raft-shape along the perpendicular direction to the tensile stress axis while in [011] orientation the g ￠ phase develops along the [010] and [100] and evolves into a raft with inclined 45° angle to the tensile stress axis. The strain rates for [001] and [011] orientations are almost equal at the earlier stage of creep. With the matrix channel broadening, the strain rate for [011] orientation increases gradually, while the creep strength decreases rapidly. Based on the evolutional rule of g ￠ phase and the creep curves, the anisotropic creep behavior is obvious at the later stage of steady-state and the tertiary creep stage
The morphology evolution and creep behavior of g ￠ phase in [001] and [011] oriented specimens of a nickel-base single crystal superalloy during the tensile creep at 1253 K and 200 MPa were investigated. SEM and TEM observation shows that the direction coarsening of precipitates is highly dependent on the crystal orientation. In [001] orientation, the g ￠ phase transits from original cuboids to the raft-shape along the perpendicular direction to the tensile stress axis while in [011] orientation the g ￠ phase develops along the [010] and [100] and evolves into a raft with inclined 45° angle to the tensile stress axis. The strain rates for [001] and [011] orientations are almost equal at the earlier stage of creep. With the matrix channel broadening, the strain rate for [011] orientation increases gradually, while the creep strength decreases rapidly. Based on the evolutional rule of g ￠ phase and the creep curves, the anisotropic creep behavior is obvious at the later stage of steady-state and the tertiary creep stage
2011, 40(9):1526-1529.
Abstract:
Cold rolled Ni-5at%W substrates with short length were annealed at different temperatures. On the basis of the results of annealing of short length substrates, the substrates with long length were annealed by reel-to-reel method. The hardness of the annealed substrates at different temperatures was analyzed. The recrystallization textures were evaluated by X-ray pole figure and the microstructure were investigated by optical microscopy. The effects of annealing temperature on the recrystalization texture were discussed. The differences of recrystallization texture between short length substrates and long length substrates were investigated. It is found that both short length substrates and long length substrates have very strong cube texture
Cold rolled Ni-5at%W substrates with short length were annealed at different temperatures. On the basis of the results of annealing of short length substrates, the substrates with long length were annealed by reel-to-reel method. The hardness of the annealed substrates at different temperatures was analyzed. The recrystallization textures were evaluated by X-ray pole figure and the microstructure were investigated by optical microscopy. The effects of annealing temperature on the recrystalization texture were discussed. The differences of recrystallization texture between short length substrates and long length substrates were investigated. It is found that both short length substrates and long length substrates have very strong cube texture
7 Microstructure and Properties of TA2 Commercially Pure Titanium Surface by Friction Stir Processing
2011, 40(9):1530-1533.
Abstract:
Friction stir processing (FSP) for TA2 commercially pure titanium was performed. The microstructure characteristics of the stir zone, the thermo-mechanically affected zone and the heat affected zone were investigated. The hardness and wear properties of the base material and the friction stir procession specimen were analyzed contrastively. The results indicate that in the surface of TA2 commercially pure titanium after FSP, the grains of the stir zone undergo plastic deformation, blending and breaking to realize the densification and homogenization of the microstructure. The microhardness of the stir zone is increased by 37.5% compared with that of the base material. When the abrasive wear cycle is 1000, 1500 and 2000 r, the abrasion loss of the stir zone is smaller than that of the base material by about 31.4%, 36.6% and 46.4%, respectively. The microhardness and wear properties of the TA2 commercially pure titanium are greatly improved
Friction stir processing (FSP) for TA2 commercially pure titanium was performed. The microstructure characteristics of the stir zone, the thermo-mechanically affected zone and the heat affected zone were investigated. The hardness and wear properties of the base material and the friction stir procession specimen were analyzed contrastively. The results indicate that in the surface of TA2 commercially pure titanium after FSP, the grains of the stir zone undergo plastic deformation, blending and breaking to realize the densification and homogenization of the microstructure. The microhardness of the stir zone is increased by 37.5% compared with that of the base material. When the abrasive wear cycle is 1000, 1500 and 2000 r, the abrasion loss of the stir zone is smaller than that of the base material by about 31.4%, 36.6% and 46.4%, respectively. The microhardness and wear properties of the TA2 commercially pure titanium are greatly improved
2011, 40(9):1534-1539.
Abstract:
The isothermal constant strain rate compression tests of a Ti3Al based alloy were conducted by THERMECMASTER-Z simulator and the deformation behavior at the temperature of 950-1350 oC and strain rate of 0.001-10 s-1 were investigated. The processing maps under these deformation conditions were constructed and the hot working parameters were then optimized based on the generated processing maps. The processing maps developed on the basis of dynamic material model exhibit following five domains. (1) The alloy exhibits domain of flow localization and adiabatic shear bands in the temperature range of 950-1100 oC and strain rate range of 0.05-10 s-1. (2) The region of flow instability occurs in the temperature range of 1100-1350 oC and strain rate range of 0.1-10 s-1. The manifestation of flow instability is non-uniform deformation of β grains. (3) The alloy undergoes dynamic recovery in the temperature region of 1250-1350oC and a strain rate below 0.01 s-1. The materials exhibit significant grain coarsening in this domain. (4) The subgrain could be found in the temperature range from 1100 oC to 1180 oC and the strain rate from 0.001 to 0.015 s-1 with a power dissipation efficiency above 0.55. (5) The deformation characteristic of the Ti3Al based alloy in the temperature ranger of 970-1010 oC and strain rate range of 0.001-0.01 s-1 is superplasticity with power dissipation efficiency above 0.5. The last two regions can be considered as the optimal parameter range of isothermal compression for Ti3Al based alloy
The isothermal constant strain rate compression tests of a Ti3Al based alloy were conducted by THERMECMASTER-Z simulator and the deformation behavior at the temperature of 950-1350 oC and strain rate of 0.001-10 s-1 were investigated. The processing maps under these deformation conditions were constructed and the hot working parameters were then optimized based on the generated processing maps. The processing maps developed on the basis of dynamic material model exhibit following five domains. (1) The alloy exhibits domain of flow localization and adiabatic shear bands in the temperature range of 950-1100 oC and strain rate range of 0.05-10 s-1. (2) The region of flow instability occurs in the temperature range of 1100-1350 oC and strain rate range of 0.1-10 s-1. The manifestation of flow instability is non-uniform deformation of β grains. (3) The alloy undergoes dynamic recovery in the temperature region of 1250-1350oC and a strain rate below 0.01 s-1. The materials exhibit significant grain coarsening in this domain. (4) The subgrain could be found in the temperature range from 1100 oC to 1180 oC and the strain rate from 0.001 to 0.015 s-1 with a power dissipation efficiency above 0.55. (5) The deformation characteristic of the Ti3Al based alloy in the temperature ranger of 970-1010 oC and strain rate range of 0.001-0.01 s-1 is superplasticity with power dissipation efficiency above 0.5. The last two regions can be considered as the optimal parameter range of isothermal compression for Ti3Al based alloy
2011, 40(9):1540-1543.
Abstract:
Raman spectroscopy was used to measure residual stress of carbon layer on SiC fibre embedded longitudinally in SiC(f)/Ti-22Al-26Nb composites with different reaction layers. By measuring the band shifts of carbon layer, the residual stress arising from thermal expansion mismatch was also determined from the SiC fibre. Results show that as the thickness of reaction layer increases the interfacial residual stress dramatically decreases. Finite element analyses have similar results with the test
Raman spectroscopy was used to measure residual stress of carbon layer on SiC fibre embedded longitudinally in SiC(f)/Ti-22Al-26Nb composites with different reaction layers. By measuring the band shifts of carbon layer, the residual stress arising from thermal expansion mismatch was also determined from the SiC fibre. Results show that as the thickness of reaction layer increases the interfacial residual stress dramatically decreases. Finite element analyses have similar results with the test
2011, 40(9):1544-1549.
Abstract:
The samples of Ti-46Al-6(Cr,Nb,Si,B) (at%), G4 alloy for short, were hot compressed in the temperature range of 1050-1250 oC at constant strain rate from 0.001~1 s-1 for high temperature flow behavior and microstructural evolution study. The results show that G4 alloy displays a flow characteristic of hardening followed by softening during hot compression. The microstructure of G4 alloy evolves from as-cast big size γ+γ/α2 to small size near-equiaxed γ+α2. Dynamic recrystallization (DRX) is the main reason that results in flow softening and macro- and micro-structure evolution of G4 alloy. Temperature and strain rate are the two main factors that influence flow softening behavior and microstructure evolution of the G4 alloy during high temperature deformation. The main transformation mechanism of the G4 alloy at elevated temperature is kinking, curving, globalizing and DRX of γ/α2 lamellae, and elongating, breaking and DRX of γ grain, with twining as an auxiliary deformation mode. The optimum temperature for hot forming of cast near lamella G4 alloy is 1150 oC, and the strain rate should not exceed 0.1 s-1
The samples of Ti-46Al-6(Cr,Nb,Si,B) (at%), G4 alloy for short, were hot compressed in the temperature range of 1050-1250 oC at constant strain rate from 0.001~1 s-1 for high temperature flow behavior and microstructural evolution study. The results show that G4 alloy displays a flow characteristic of hardening followed by softening during hot compression. The microstructure of G4 alloy evolves from as-cast big size γ+γ/α2 to small size near-equiaxed γ+α2. Dynamic recrystallization (DRX) is the main reason that results in flow softening and macro- and micro-structure evolution of G4 alloy. Temperature and strain rate are the two main factors that influence flow softening behavior and microstructure evolution of the G4 alloy during high temperature deformation. The main transformation mechanism of the G4 alloy at elevated temperature is kinking, curving, globalizing and DRX of γ/α2 lamellae, and elongating, breaking and DRX of γ grain, with twining as an auxiliary deformation mode. The optimum temperature for hot forming of cast near lamella G4 alloy is 1150 oC, and the strain rate should not exceed 0.1 s-1
2011, 40(9):1550-1554.
Abstract:
TA2 titanium substrate was etched by oxalic acid, hydrochloride acid and sulfuric acid, respectively, under the condition of the same acidity and temperature. The effects of various acids treatment on the properties of Ti substrate and the as-prepared electrodes were investigated. The results indicate that the mass loss rate of the titanium substrate treated by oxide acid and sulfuric acid are higher than that of the substrate treated by hydrochloride acid. The OM and SEM images show that the titanium substrate treated by oxide acid has the best surface morphology after the etching process, with the fine and uniform scores. The accelerated test life of the dimensional stable anode prepared from the titanium substrate treated by oxide acid is the longest among the three types’ electrodes. The oxygen evolution potentials of the three types’ electrodes are nearly the same, which means that the acid treatment has a slight influence on the oxygen evolution potential of the electrodes
TA2 titanium substrate was etched by oxalic acid, hydrochloride acid and sulfuric acid, respectively, under the condition of the same acidity and temperature. The effects of various acids treatment on the properties of Ti substrate and the as-prepared electrodes were investigated. The results indicate that the mass loss rate of the titanium substrate treated by oxide acid and sulfuric acid are higher than that of the substrate treated by hydrochloride acid. The OM and SEM images show that the titanium substrate treated by oxide acid has the best surface morphology after the etching process, with the fine and uniform scores. The accelerated test life of the dimensional stable anode prepared from the titanium substrate treated by oxide acid is the longest among the three types’ electrodes. The oxygen evolution potentials of the three types’ electrodes are nearly the same, which means that the acid treatment has a slight influence on the oxygen evolution potential of the electrodes
2011, 40(9):1555-1560.
Abstract:
A macro-meso multi-scale method was proposed to investigate the quasi-static and dynamic mechanical behavior of particle-reinforced titanium matrix composites based on a fixed point iteration method. By using this method, the macro-mechanical properties of the composites can be connected with the microstructure. The physical boundary conditions can be obtained for unit cells with the fixed point iteration method from the macro point of view. Dozens of cases have been performed to simulate the macro-mechanical characteristics of the composites by applying these displacement constraint conditions to the unit cells. Based on the comparison of numerical predictions with experimental results, the effects of particle shape, particle volume fraction, particle size and interface strength on the TiC particle-reinforced titanium matrix composites under quasi-static and dynamic loadings are predicted, which provides a basis for the optimal design of particle-reinforced titanium matrix composites
A macro-meso multi-scale method was proposed to investigate the quasi-static and dynamic mechanical behavior of particle-reinforced titanium matrix composites based on a fixed point iteration method. By using this method, the macro-mechanical properties of the composites can be connected with the microstructure. The physical boundary conditions can be obtained for unit cells with the fixed point iteration method from the macro point of view. Dozens of cases have been performed to simulate the macro-mechanical characteristics of the composites by applying these displacement constraint conditions to the unit cells. Based on the comparison of numerical predictions with experimental results, the effects of particle shape, particle volume fraction, particle size and interface strength on the TiC particle-reinforced titanium matrix composites under quasi-static and dynamic loadings are predicted, which provides a basis for the optimal design of particle-reinforced titanium matrix composites
2011, 40(9):1561-1564.
Abstract:
An high temperature quasistatic compression test (0.01 s-1) and a dynamic shearing experiment (103 s-1) on TC6 titanium alloy were performed by the gleeble-1500-type thermal simulation testing machine and a split Hopkinson bar process, respectively. Microstructure evolution of TC6 titanium alloy deformed under the condition of high temperature and high strain rate were contrastively investigated by means of optical microscope and transmission electron microscopy. Results show that the microstructure evolution of TC6 titanium alloy deformed at high temperatures is observably different from that at high strain-rate. The former includes four stages, i.e. deforming of equiaxed-type α phase to lath-shape α phase, breakdown of lath-shape α phase and simultaneous appearing and growth of dynamically recrystallized grains and phase transformation of α/β. The later goes through three stages, i.e. deforming of equiaxed-type α phase to lath-shape α phase, and then to lathy α phase due to rapid movement of dislocation, breakdown of lathy α phase and appearing of a few dynamically recrystallized grains. Under the two conditions of deforming, there is dynamically recrystallized grains occurring without exception, but there is a greater amount of dynamically recrystallized grains under the condition of high temperature and the dynamically recrystallized grains have grown up with sizes of 3-5 μm approximately. Whenas there are a few dynamically recrystallized grains that never grow up at high strain-rate with sizes of 0.1-0.2 μm approximately
An high temperature quasistatic compression test (0.01 s-1) and a dynamic shearing experiment (103 s-1) on TC6 titanium alloy were performed by the gleeble-1500-type thermal simulation testing machine and a split Hopkinson bar process, respectively. Microstructure evolution of TC6 titanium alloy deformed under the condition of high temperature and high strain rate were contrastively investigated by means of optical microscope and transmission electron microscopy. Results show that the microstructure evolution of TC6 titanium alloy deformed at high temperatures is observably different from that at high strain-rate. The former includes four stages, i.e. deforming of equiaxed-type α phase to lath-shape α phase, breakdown of lath-shape α phase and simultaneous appearing and growth of dynamically recrystallized grains and phase transformation of α/β. The later goes through three stages, i.e. deforming of equiaxed-type α phase to lath-shape α phase, and then to lathy α phase due to rapid movement of dislocation, breakdown of lathy α phase and appearing of a few dynamically recrystallized grains. Under the two conditions of deforming, there is dynamically recrystallized grains occurring without exception, but there is a greater amount of dynamically recrystallized grains under the condition of high temperature and the dynamically recrystallized grains have grown up with sizes of 3-5 μm approximately. Whenas there are a few dynamically recrystallized grains that never grow up at high strain-rate with sizes of 0.1-0.2 μm approximately
2011, 40(9):1565-1567.
Abstract:
Ti-47Al-2Cr-2Nb-xB (x=0, 0.15, 0.8, 1.5) (at%) crisscross casting with different thickness (2, 5, 10 and 20 mm) were prepared by a vacuum induction skull furnace. Influences of the cooling rate and the boron concentration on the boride shape and the grain size of the casting were studied by means of stereo microscope and scanning electron microscopy (SEM). The results show that the higher boron concentration and the faster cooling rate lead to smaller grain size. Waved-flake borides change into stick- or plate-like ones when the boron concentration increases. Boride size of Ti-47Al-2Cr-2Nb-0.8B casting is reduced with the cooling rate decreasing, but the change of boride size of Ti-47Al-2Cr-2Nb-0.15B and Ti-47Al-2Cr-2Nb-1.5B casting is unobvious
Ti-47Al-2Cr-2Nb-xB (x=0, 0.15, 0.8, 1.5) (at%) crisscross casting with different thickness (2, 5, 10 and 20 mm) were prepared by a vacuum induction skull furnace. Influences of the cooling rate and the boron concentration on the boride shape and the grain size of the casting were studied by means of stereo microscope and scanning electron microscopy (SEM). The results show that the higher boron concentration and the faster cooling rate lead to smaller grain size. Waved-flake borides change into stick- or plate-like ones when the boron concentration increases. Boride size of Ti-47Al-2Cr-2Nb-0.8B casting is reduced with the cooling rate decreasing, but the change of boride size of Ti-47Al-2Cr-2Nb-0.15B and Ti-47Al-2Cr-2Nb-1.5B casting is unobvious
2011, 40(9):1570-1573.
Abstract:
The leftover materials of NiTi shape memory alloy were remelted via vacuum induction melting in a graphite crucible. After rolling, the remelted alloy plates were aged at different temperatures and their room temperature mechanical properties were investigated. Results show that after remelting of the leftover materials of NiTi shape memory alloys, their yield strength and tensile strength are increased to different extents, while the elongation is only increased a little. The shape recovery rate by stress-induced martensite transformation is decreased. At the same time, the ability of plastic deformation becomes poorer with the aging temperature increasing. On the whole, the elongation provided by reorientaion of R phase is longer than that of another NiTi shape memory alloy melted from electrolytic nickel and sponge titanium
The leftover materials of NiTi shape memory alloy were remelted via vacuum induction melting in a graphite crucible. After rolling, the remelted alloy plates were aged at different temperatures and their room temperature mechanical properties were investigated. Results show that after remelting of the leftover materials of NiTi shape memory alloys, their yield strength and tensile strength are increased to different extents, while the elongation is only increased a little. The shape recovery rate by stress-induced martensite transformation is decreased. At the same time, the ability of plastic deformation becomes poorer with the aging temperature increasing. On the whole, the elongation provided by reorientaion of R phase is longer than that of another NiTi shape memory alloy melted from electrolytic nickel and sponge titanium
2011, 40(9):1574-1579.
Abstract:
By means of measuring creep curves under the applied stress of 137 MPa at 1040 oC and observing the microstructure by SEM after the alloy was heat treated and crept, the microstructure evolution of [011] orientation single crystal nickel-base superalloy during tensile creep was investigated, and the effect factors of the evolution regularity was analyzed. Results show that, after full heat treatment, the microstructure of [011] oriented single crystal nickel-base superalloy consists of the cubic γ′ phase embedded coherently in the γ matrix, regularly arranged along the <100> orientation. During tensile creep, the cubic γ′ phase in the alloy is transformed into the strip-like rafted structure along the direction parallel to [001] orientation. In the action of the applied tensile stress along the [011] orientation, the extrusion stress is applied on the g phase and (100) crystal plane of the cubic γ′ phase to generate the constricted strain of the lattice, which may exclude the Al and Ta atoms with bigger radius. Whereas, the expanding lattice strain appearing on the (001) crystal plane of the cubic γ′ phase may trap the Al and Ta atoms with bigger radius. Therefore, the cubic γ′ phase is directionally grown into the strip-like rafted structure along the [001] orientation. In the action of the applied stress, the change of the strain energy density in the different interfaces of the cubic γ′/γ phases is thought to be the driving force of the element diffusion and the directional coarsening of γ′ phase
By means of measuring creep curves under the applied stress of 137 MPa at 1040 oC and observing the microstructure by SEM after the alloy was heat treated and crept, the microstructure evolution of [011] orientation single crystal nickel-base superalloy during tensile creep was investigated, and the effect factors of the evolution regularity was analyzed. Results show that, after full heat treatment, the microstructure of [011] oriented single crystal nickel-base superalloy consists of the cubic γ′ phase embedded coherently in the γ matrix, regularly arranged along the <100> orientation. During tensile creep, the cubic γ′ phase in the alloy is transformed into the strip-like rafted structure along the direction parallel to [001] orientation. In the action of the applied tensile stress along the [011] orientation, the extrusion stress is applied on the g phase and (100) crystal plane of the cubic γ′ phase to generate the constricted strain of the lattice, which may exclude the Al and Ta atoms with bigger radius. Whereas, the expanding lattice strain appearing on the (001) crystal plane of the cubic γ′ phase may trap the Al and Ta atoms with bigger radius. Therefore, the cubic γ′ phase is directionally grown into the strip-like rafted structure along the [001] orientation. In the action of the applied stress, the change of the strain energy density in the different interfaces of the cubic γ′/γ phases is thought to be the driving force of the element diffusion and the directional coarsening of γ′ phase
2011, 40(9):1580-1583.
Abstract:
Tungsten fiber reinforced Cu82Al10Fe4Ni4 composites were prepared by a melt infiltrating casting method. Dynamic compression behavior and fracture characteristics were investigated by Split Hopkinson Pressure Bar (SHPB) and scanning electron microscopy (SEM). The results show that the interface between tungsten fibers and the matrix alloy is compact, and it exhibits high strength under dynamic compression. The composites create some plastic deformation and cracks under dynamic compression at strain rate of 2000 s-1. The dynamic compressive strength of the composites is 2500 MPa under dynamic compression at strain rate of 3000 s-1, and the failure modes of the composites include splitting and buckling of tungsten fiber and abruption of the matrix alloy. Meantime, the fracture surface creates lots of melting bands, which change the fracture mode of the composites and accelerate its failure
Tungsten fiber reinforced Cu82Al10Fe4Ni4 composites were prepared by a melt infiltrating casting method. Dynamic compression behavior and fracture characteristics were investigated by Split Hopkinson Pressure Bar (SHPB) and scanning electron microscopy (SEM). The results show that the interface between tungsten fibers and the matrix alloy is compact, and it exhibits high strength under dynamic compression. The composites create some plastic deformation and cracks under dynamic compression at strain rate of 2000 s-1. The dynamic compressive strength of the composites is 2500 MPa under dynamic compression at strain rate of 3000 s-1, and the failure modes of the composites include splitting and buckling of tungsten fiber and abruption of the matrix alloy. Meantime, the fracture surface creates lots of melting bands, which change the fracture mode of the composites and accelerate its failure
2011, 40(9):1584-1588.
Abstract:
The influences of W content and friction condition on the tribological properties of W-doped diamond-like carbon (DLC) coatings were studied. Results show that the friction coefficients of W-doped DLC coatings is augmented with the W content increasing; the W-doped DLC coatings with a W content of 3.1% exhibit the best film/substrate adhesion and wear resistance. Under the dry friction condition, the friction coefficients of W-doped DLC coatings with a low W content are increased with the rise of load while low friction coefficients of W-doped DLC coatings with a high W content are found at a high load; the friction coefficients are increased with the rotation rate increasing for the DLC coatings with a high W content, but the influence of the rotation rate on the friction coefficients of un-doped DLC coatings is unobvious. The wear of W-doped DLC coatings are produced by the micro-fracture and peeling in the coatings during the indentation of hard Si3N4 ball into the sample surface
The influences of W content and friction condition on the tribological properties of W-doped diamond-like carbon (DLC) coatings were studied. Results show that the friction coefficients of W-doped DLC coatings is augmented with the W content increasing; the W-doped DLC coatings with a W content of 3.1% exhibit the best film/substrate adhesion and wear resistance. Under the dry friction condition, the friction coefficients of W-doped DLC coatings with a low W content are increased with the rise of load while low friction coefficients of W-doped DLC coatings with a high W content are found at a high load; the friction coefficients are increased with the rotation rate increasing for the DLC coatings with a high W content, but the influence of the rotation rate on the friction coefficients of un-doped DLC coatings is unobvious. The wear of W-doped DLC coatings are produced by the micro-fracture and peeling in the coatings during the indentation of hard Si3N4 ball into the sample surface
2011, 40(9):1589-1593.
Abstract:
The galvanic corrosion of an AZ91D magnesium alloy coupled with 316L stainless steel using accelerated testing in salt spray fog has been investigated by using the scanning Kelvin probe (SKP) technique. The results show that the galvanic effects for AZ91D magnesium alloys are affected by the potential difference between anode and cathode by analyzing corrosion products and SKP Volta potential maps. The galvanic effect of AZ91D magnesium alloy coupled with 316L stainless steel is very significant during accelerated testing in the initial stage of salt spray fog because the potential difference between AZ91D magnesium alloy and 316L stainless steel is about –1.28 V. The galvanic corrosion occurs mainly in the interface near AZ91D magnesium alloy, and 316L stainless steel has no obvious corrosion. With the salt spray test time increasing, the corrosion of the AZ91D magnesium alloy is accelerated and the coverage area of corrosion products expanded. The Volta potential difference of galvanic sample increases from –1.29 V to –1.53 V after 24 h salt spray test. The galvanic corrosion effect of AZ91D magnesium alloy is increased. The corrosion products of AZ91D magnesium alloy have a protective effect. The galvanic corrosion effect is reduced when the corrosion product increases to cover the surface of the specimen
The galvanic corrosion of an AZ91D magnesium alloy coupled with 316L stainless steel using accelerated testing in salt spray fog has been investigated by using the scanning Kelvin probe (SKP) technique. The results show that the galvanic effects for AZ91D magnesium alloys are affected by the potential difference between anode and cathode by analyzing corrosion products and SKP Volta potential maps. The galvanic effect of AZ91D magnesium alloy coupled with 316L stainless steel is very significant during accelerated testing in the initial stage of salt spray fog because the potential difference between AZ91D magnesium alloy and 316L stainless steel is about –1.28 V. The galvanic corrosion occurs mainly in the interface near AZ91D magnesium alloy, and 316L stainless steel has no obvious corrosion. With the salt spray test time increasing, the corrosion of the AZ91D magnesium alloy is accelerated and the coverage area of corrosion products expanded. The Volta potential difference of galvanic sample increases from –1.29 V to –1.53 V after 24 h salt spray test. The galvanic corrosion effect of AZ91D magnesium alloy is increased. The corrosion products of AZ91D magnesium alloy have a protective effect. The galvanic corrosion effect is reduced when the corrosion product increases to cover the surface of the specimen
2011, 40(9):1594-1599.
Abstract:
Microstructures and mechanical properties of the Mg9AlZnY magnesium alloy in lost foam casting were researched through adding rare-earth element Gd. The results show that the β-Mg17Al12 phase of Mg9AlZnY alloy is significantly reduced with the increase of Gd element, and the formation of β-Mg17Al12 phase turns into an intermittent and granular structure from the continuous network structure. Microstructure of the Mg9AlZnY alloys containing Gd is mainly composed of the α-Mg solid solution, β-Mg17Al12 phase and a small number of rod-like Al2Y and block-like Al2Gd phases which are distributed over grain boundaries of the α-Mg phase. The Al2Y and Al2Gd phases, which pin the grain boundary at high temperature and prevent grain boundary from sliding, have good thermal stability, increasing the high-temperature strength of the grain boundary. After T6 heat treatment, the tensile strength at room temperature is 235 MPa and the high-temperature strength at 200 oC is 156 MPa when the rare-earth element Gd is about 0.9%, which is increased by 11.9% and 28.9% compared with those of Mg9AlZnY alloy, respectively
Microstructures and mechanical properties of the Mg9AlZnY magnesium alloy in lost foam casting were researched through adding rare-earth element Gd. The results show that the β-Mg17Al12 phase of Mg9AlZnY alloy is significantly reduced with the increase of Gd element, and the formation of β-Mg17Al12 phase turns into an intermittent and granular structure from the continuous network structure. Microstructure of the Mg9AlZnY alloys containing Gd is mainly composed of the α-Mg solid solution, β-Mg17Al12 phase and a small number of rod-like Al2Y and block-like Al2Gd phases which are distributed over grain boundaries of the α-Mg phase. The Al2Y and Al2Gd phases, which pin the grain boundary at high temperature and prevent grain boundary from sliding, have good thermal stability, increasing the high-temperature strength of the grain boundary. After T6 heat treatment, the tensile strength at room temperature is 235 MPa and the high-temperature strength at 200 oC is 156 MPa when the rare-earth element Gd is about 0.9%, which is increased by 11.9% and 28.9% compared with those of Mg9AlZnY alloy, respectively
2011, 40(9):1600-1604.
Abstract:
In order to join wrought magnesium alloy AZ31B plates, an Al matrix filler metal was developed to join them by means of high-frequency induction brazing. The microstructure and phase constitution of the brazed joint were investigated by scanning electron microscopy, X-ray diffraction and X-ray energy dispersive spectroscopy. The mechanical properties and microhardness of the brazed joint were also tested. The results show that the single Mg32(Al,Zn)49 phase in the original filler metal is consumed after the soldering process; moreover, α-Mg solid solution and β-Mg17(Al,Zn)12 phase are formed in brazing region due to the intensive alloying between the molten filler metal and the base metal in the process of brazing. The average tensile strength of the butted joint is 71 MPa and the average shearing strength of the overlapped joint is 44 MPa. The fracture surface of the brazed joint exhibits an intergranular fracture feature and the crack originates from the hard β-Mg17(Al,Zn)12 phase
In order to join wrought magnesium alloy AZ31B plates, an Al matrix filler metal was developed to join them by means of high-frequency induction brazing. The microstructure and phase constitution of the brazed joint were investigated by scanning electron microscopy, X-ray diffraction and X-ray energy dispersive spectroscopy. The mechanical properties and microhardness of the brazed joint were also tested. The results show that the single Mg32(Al,Zn)49 phase in the original filler metal is consumed after the soldering process; moreover, α-Mg solid solution and β-Mg17(Al,Zn)12 phase are formed in brazing region due to the intensive alloying between the molten filler metal and the base metal in the process of brazing. The average tensile strength of the butted joint is 71 MPa and the average shearing strength of the overlapped joint is 44 MPa. The fracture surface of the brazed joint exhibits an intergranular fracture feature and the crack originates from the hard β-Mg17(Al,Zn)12 phase
2011, 40(9):1605-1609.
Abstract:
Based on the microscopic phase-field kinetic model, the growth of the ordered phase and the growth direction change of the structure during the early precipitation for Ni-Al-V alloys with different components when aging were investigated. The results show that during the early precipitation the competitive growth between ordered phases may greatly influence the shape and growth direction of alloys. Under the condition of certain temperature and elastic stress, when the Al content is lower, DO22 ordered phases precipitate first, which are numerous and small, the rafting of the ordered phase is not obvious and there is not remarkable rafting for the whole alloys. When the Al content a little higher, L12 phases precipitate first, DO22 phases become less and bigger, and the structure preferentially grows along [100]. When the Al content is much higher, L12 phases precipitate first, and the DO22 phase becomes less and bigger continuously, while the structure exhibits a strong rafting trend along [100]. Aged at a lower temperature, L12 ordered phase precipitates ahead and the rafting trend is weaker
Based on the microscopic phase-field kinetic model, the growth of the ordered phase and the growth direction change of the structure during the early precipitation for Ni-Al-V alloys with different components when aging were investigated. The results show that during the early precipitation the competitive growth between ordered phases may greatly influence the shape and growth direction of alloys. Under the condition of certain temperature and elastic stress, when the Al content is lower, DO22 ordered phases precipitate first, which are numerous and small, the rafting of the ordered phase is not obvious and there is not remarkable rafting for the whole alloys. When the Al content a little higher, L12 phases precipitate first, DO22 phases become less and bigger, and the structure preferentially grows along [100]. When the Al content is much higher, L12 phases precipitate first, and the DO22 phase becomes less and bigger continuously, while the structure exhibits a strong rafting trend along [100]. Aged at a lower temperature, L12 ordered phase precipitates ahead and the rafting trend is weaker
2011, 40(9):1610-1615.
Abstract:
Effect of Fe and C doping via ion implantation on the lattice distortion of He ion implanted Al surface was studied by X-ray diffraction (XRD). The results show that the pre-doped Fe and C play an important part in the lattice distortion of Al surface, and the influence extent depends on the doping fluence. With the increase of the fluence of pre-doped Fe, the lattice distortion of Al surface decreases first and then increases, indicating that Fe doping of small fluence is beneficial for the reduction of lattice distortion of He implanted Al. C doping can further reduce the lattice distortion caused by the earlier Fe doping, and the reduction extent increases with the fluence of doped C increasing. It is concluded that small fluence of Fe and high fluence of C co-doping can effectively reduce the lattice distortion of the He implanted Al surface
Effect of Fe and C doping via ion implantation on the lattice distortion of He ion implanted Al surface was studied by X-ray diffraction (XRD). The results show that the pre-doped Fe and C play an important part in the lattice distortion of Al surface, and the influence extent depends on the doping fluence. With the increase of the fluence of pre-doped Fe, the lattice distortion of Al surface decreases first and then increases, indicating that Fe doping of small fluence is beneficial for the reduction of lattice distortion of He implanted Al. C doping can further reduce the lattice distortion caused by the earlier Fe doping, and the reduction extent increases with the fluence of doped C increasing. It is concluded that small fluence of Fe and high fluence of C co-doping can effectively reduce the lattice distortion of the He implanted Al surface
2011, 40(9):1616-1620.
Abstract:
Gra./Cu composites and CNTs/Cu composites were prepared by powder metallurgy. Chopping current and cathode spot movements of the 2 kinds of Cu matrix composites in vacuum were investigated. The results show that the vacuum arc of CNTs/Cu is more stable and dispersive, and the chopping current is less than that of Gra./Cu. For CNTs/Cu the size of cathode spot craters is 0.1-5 μm in diameter, while for Gra./Cu is between 10 and 100 μm. The common characteristics are that cathode spot initiates selectively on the Cu phases and walks randomly on the surface of the Cu matrix composites. It is concluded that CNTs/Cu has an higher arc erosion resistance than Gra./Cu, and CNTs can effectively increase stability and lower chopping current of the Cu matrix composites.
Gra./Cu composites and CNTs/Cu composites were prepared by powder metallurgy. Chopping current and cathode spot movements of the 2 kinds of Cu matrix composites in vacuum were investigated. The results show that the vacuum arc of CNTs/Cu is more stable and dispersive, and the chopping current is less than that of Gra./Cu. For CNTs/Cu the size of cathode spot craters is 0.1-5 μm in diameter, while for Gra./Cu is between 10 and 100 μm. The common characteristics are that cathode spot initiates selectively on the Cu phases and walks randomly on the surface of the Cu matrix composites. It is concluded that CNTs/Cu has an higher arc erosion resistance than Gra./Cu, and CNTs can effectively increase stability and lower chopping current of the Cu matrix composites.
2011, 40(9):1621-1624.
Abstract:
Mo-Cu alloys with different Fe content were prepared by an infiltration method. The microstructure and distribution of Fe of the alloys were analyzed by field-emission scanning electron microscope (FESEM) and energy disperse spectroscopy (EDS). The influence of Fe content on the density, thermal conductivity, electrical conductivity, hardness and microstructure was investigated. The results show that 1% Fe addition (mass fraction) increases the density and the hardness of the Mo-Cu alloys, but decreases thermal conductivity and electrical conductivity; meanwhile the microstructure becomes more compact, and Cu distributes in the form of mesh, and Mo skeleton sintering necks become bigger. However, too much Fe is not conducive to the improvement of properties
Mo-Cu alloys with different Fe content were prepared by an infiltration method. The microstructure and distribution of Fe of the alloys were analyzed by field-emission scanning electron microscope (FESEM) and energy disperse spectroscopy (EDS). The influence of Fe content on the density, thermal conductivity, electrical conductivity, hardness and microstructure was investigated. The results show that 1% Fe addition (mass fraction) increases the density and the hardness of the Mo-Cu alloys, but decreases thermal conductivity and electrical conductivity; meanwhile the microstructure becomes more compact, and Cu distributes in the form of mesh, and Mo skeleton sintering necks become bigger. However, too much Fe is not conducive to the improvement of properties
2011, 40(9):1625-1628.
Abstract:
Kissinger, Ozawa and MKN methods were adopted to study the effect of Fe/Co ratios on the crystallization behavior in (FexCo1-x)72B19.2Si4.8Nb4 bulk amorphous alloys. The results show that when x ranges from 0.3 to 0.7, the as-cast (FexCo1-x)72B19.2Si4.8Nb4 alloy rods with a diameter of 2 mm are in an amorphous state. The glass transition temperature Tg, onset temperature of crystallization Tx and crystallization peak temperature Tp move towards to the higher temperature regions with increasing the heating rates. The result differences of activation energies calculated by Kissinger, Ozawa and MKN methods are not too much, among which, the results calculated by Kissinger and MKN methods are slightly larger than those calculated by Ozawa method and Ex>Ep>Eg. With increasing the Fe content, the apparatus crystallization activation energy Ex increases firstly, and then decreases, while the maximum value of local crystallization activation energy Eo presents a decline trend
Kissinger, Ozawa and MKN methods were adopted to study the effect of Fe/Co ratios on the crystallization behavior in (FexCo1-x)72B19.2Si4.8Nb4 bulk amorphous alloys. The results show that when x ranges from 0.3 to 0.7, the as-cast (FexCo1-x)72B19.2Si4.8Nb4 alloy rods with a diameter of 2 mm are in an amorphous state. The glass transition temperature Tg, onset temperature of crystallization Tx and crystallization peak temperature Tp move towards to the higher temperature regions with increasing the heating rates. The result differences of activation energies calculated by Kissinger, Ozawa and MKN methods are not too much, among which, the results calculated by Kissinger and MKN methods are slightly larger than those calculated by Ozawa method and Ex>Ep>Eg. With increasing the Fe content, the apparatus crystallization activation energy Ex increases firstly, and then decreases, while the maximum value of local crystallization activation energy Eo presents a decline trend
2011, 40(9):1629-1631.
Abstract:
The transportation behavior of Au(III) through a dispersion supported liquid membrane (DSLM) consisting of tri-n-octylamine in kerosene, supported on the polyvinylidene fluoride membrane (PVDF), was studied. The effects of HCl concentrations in the feed phase, volume ratio of liquid membrane phase to strip phase, and concentrations of KCN in the strip phase were also researched. The results show that gold ion can be transported effectively when the concentration of HCl in the feed phase is 2.0 mol/L, the volume ratio is 40:20, and the concentration of KCN in the strip phase is 0.5 mol/L
The transportation behavior of Au(III) through a dispersion supported liquid membrane (DSLM) consisting of tri-n-octylamine in kerosene, supported on the polyvinylidene fluoride membrane (PVDF), was studied. The effects of HCl concentrations in the feed phase, volume ratio of liquid membrane phase to strip phase, and concentrations of KCN in the strip phase were also researched. The results show that gold ion can be transported effectively when the concentration of HCl in the feed phase is 2.0 mol/L, the volume ratio is 40:20, and the concentration of KCN in the strip phase is 0.5 mol/L
2011, 40(9):1633-1637.
Abstract:
A new metastable β titanium alloy, Ti-25Nb-10Ta-1Zr-0.2Fe, was designed for biomedical applications. The alloy ingot was prepared by vacuum consumable electrode arc melting. The solid-solution aging behavior of the alloy was investigated. The phase composition and the microstructure were studied by XRD, TEM and SEM. The tensile strength after aging and the hardness for different aging time were tested. Results show that only the α″ phase is found after solid solution treatment at 800 oC for 1 h. The ω phase and β phase are observed when the alloy is subjected to aging treatment at 400 oC for 0.5 h. The ω phase, as a brittle phase, keeps a high volume fraction during the aging treatment, which leads to a sharp increase of the Vicker hardness. In this case, the tensile strength of the alloy decreases dramatically to only about 400 MPa, which is much smaller than that of the specimen in the cold-rolled condition (about 750 MPa). Hence, a large mount of ω phase decreases the tensile property of the newly designed alloy Ti-25Nb-10Ta-1Zr-0.2Fe
A new metastable β titanium alloy, Ti-25Nb-10Ta-1Zr-0.2Fe, was designed for biomedical applications. The alloy ingot was prepared by vacuum consumable electrode arc melting. The solid-solution aging behavior of the alloy was investigated. The phase composition and the microstructure were studied by XRD, TEM and SEM. The tensile strength after aging and the hardness for different aging time were tested. Results show that only the α″ phase is found after solid solution treatment at 800 oC for 1 h. The ω phase and β phase are observed when the alloy is subjected to aging treatment at 400 oC for 0.5 h. The ω phase, as a brittle phase, keeps a high volume fraction during the aging treatment, which leads to a sharp increase of the Vicker hardness. In this case, the tensile strength of the alloy decreases dramatically to only about 400 MPa, which is much smaller than that of the specimen in the cold-rolled condition (about 750 MPa). Hence, a large mount of ω phase decreases the tensile property of the newly designed alloy Ti-25Nb-10Ta-1Zr-0.2Fe
2011, 40(9):1638-1642.
Abstract:
The Ti/Sb-SnO2 electrode and Ti/Sb-SnO2/Ce electrode were prepared by thermal decomposition. The surface morphology, phase composition and electrochemical performance of the electrodes were analyzed by SEM, EDS, XRD and CHI. Results show that SnO2 crystal cells form on the surface of the Ti/Sb-SnO2 electrode, while SnO2 grains are refined obviously due to the Ce modification and SnO2 diffraction peaks becomes stronger and broader. The Ti/Sb-SnO2/Ce electrode has the largest peak current and its surface stability and catalytic activity are enhanced greatly. Under the optimal conditions, the removal rates of orange G by Ti/Sb-SnO2/Ce, Ti/Sb-SnO2 and Ti electrodes are 94.9%, 61.9% and 46.6%, respectively, and the degradation processes follow first order reaction kinetics. The rate constants of Ti/Sb-SnO2/Ce, Ti/Sb-SnO2 and Ti electrodes are 0.1971, 0.0633 and 0.0289 min-1, respectively. The rate constant of Ti/Sb-SnO2/Ce electrode is three times of that of Ti/Sb-SnO2 electrode and seven times of that of Ti electrode. Therefore, the electro-catalytic oxidative characteristic of Ce modified Ti/Sb-SnO2 electrode is the best.
The Ti/Sb-SnO2 electrode and Ti/Sb-SnO2/Ce electrode were prepared by thermal decomposition. The surface morphology, phase composition and electrochemical performance of the electrodes were analyzed by SEM, EDS, XRD and CHI. Results show that SnO2 crystal cells form on the surface of the Ti/Sb-SnO2 electrode, while SnO2 grains are refined obviously due to the Ce modification and SnO2 diffraction peaks becomes stronger and broader. The Ti/Sb-SnO2/Ce electrode has the largest peak current and its surface stability and catalytic activity are enhanced greatly. Under the optimal conditions, the removal rates of orange G by Ti/Sb-SnO2/Ce, Ti/Sb-SnO2 and Ti electrodes are 94.9%, 61.9% and 46.6%, respectively, and the degradation processes follow first order reaction kinetics. The rate constants of Ti/Sb-SnO2/Ce, Ti/Sb-SnO2 and Ti electrodes are 0.1971, 0.0633 and 0.0289 min-1, respectively. The rate constant of Ti/Sb-SnO2/Ce electrode is three times of that of Ti/Sb-SnO2 electrode and seven times of that of Ti electrode. Therefore, the electro-catalytic oxidative characteristic of Ce modified Ti/Sb-SnO2 electrode is the best.
2011, 40(9):1643-1647.
Abstract:
Ultrafine/nanocrystalline W-20Cu (mass fraction) composite powders were synthesized by sol-spray drying and subsequent hydrogen reduction process. The powders compacts were sintered at various sintering temperatures for different holding time and then were rapidly quenched in water. The sintering densification and microstructure evolution were investigated. The results show that significant densification occurs at the sintering temperature ranging from 1000 to 1200 oC and 96.4% theoretical density can be realized when sintered at 1200 oC for 60 min. When the sintering temperature is further elevated to 1420 oC and the holding time is 90 min, the relative density of the sintered compacts exceeds the level of 99%. In the range of 1100-1420 oC, the activation energy of sintering densification decreases with the sintering temperature increasing and the value decreases from 276.3 kJ/mol at 1100 oC to 29.1 kJ/mol at 1420 oC. There is no obvious grain growth during the sintering stage below 1200 oC, whereas the grain coarsening is very rapid when the sintering temperature is above 1300 oC. As the sintering temperature increasing, the tungsten grains become spherical. In addition, the grain coarsening at the temperature of 1420 oC is in good agreement with the Ostwald mechanism and the grain coarsening kinetic coefficient is 0.024 μm3/min
Ultrafine/nanocrystalline W-20Cu (mass fraction) composite powders were synthesized by sol-spray drying and subsequent hydrogen reduction process. The powders compacts were sintered at various sintering temperatures for different holding time and then were rapidly quenched in water. The sintering densification and microstructure evolution were investigated. The results show that significant densification occurs at the sintering temperature ranging from 1000 to 1200 oC and 96.4% theoretical density can be realized when sintered at 1200 oC for 60 min. When the sintering temperature is further elevated to 1420 oC and the holding time is 90 min, the relative density of the sintered compacts exceeds the level of 99%. In the range of 1100-1420 oC, the activation energy of sintering densification decreases with the sintering temperature increasing and the value decreases from 276.3 kJ/mol at 1100 oC to 29.1 kJ/mol at 1420 oC. There is no obvious grain growth during the sintering stage below 1200 oC, whereas the grain coarsening is very rapid when the sintering temperature is above 1300 oC. As the sintering temperature increasing, the tungsten grains become spherical. In addition, the grain coarsening at the temperature of 1420 oC is in good agreement with the Ostwald mechanism and the grain coarsening kinetic coefficient is 0.024 μm3/min
2011, 40(9):1648-1652.
Abstract:
Mg2Ni-type Mg2-xLaxNi (x=0, 0.2, 0.4, 0.6) hydrogen storage alloys were prepared by casting and rapid quenching, respectively. The microstructures of the as-cast and quenched alloys were studied by XRD, SEM and HRTEM. Results show that no amorphous phase forms in the as-quenched La-free alloy, but the as-quenched alloys containing La hold a major amorphous phase. Thermal stability of the as-quenched alloys was studied by DSC, and the results show that La content and the quenching rate induce a negligible influence on the crystallization temperature of the amorphous phase. The electrochemical measurement shows that the discharge capacity of the as-cast alloys grows with the increase of La content, while the as-quenched alloys obtain the maximum discharge capacities with the variation of La content. The substitution of La for Mg markedly enhances the cycle stability of the as-cast and quenched alloys
Mg2Ni-type Mg2-xLaxNi (x=0, 0.2, 0.4, 0.6) hydrogen storage alloys were prepared by casting and rapid quenching, respectively. The microstructures of the as-cast and quenched alloys were studied by XRD, SEM and HRTEM. Results show that no amorphous phase forms in the as-quenched La-free alloy, but the as-quenched alloys containing La hold a major amorphous phase. Thermal stability of the as-quenched alloys was studied by DSC, and the results show that La content and the quenching rate induce a negligible influence on the crystallization temperature of the amorphous phase. The electrochemical measurement shows that the discharge capacity of the as-cast alloys grows with the increase of La content, while the as-quenched alloys obtain the maximum discharge capacities with the variation of La content. The substitution of La for Mg markedly enhances the cycle stability of the as-cast and quenched alloys
2011, 40(9):1653-1657.
Abstract:
Mg95Ni5-x%TiFe0.8Mn0.2Zr0.05 (x = 0, 10, 20, 30) (mass fraction) composites were prepared by hydriding combustion synthesis (HCS) and the products were mechanically milled (MM) to obtain Mg-based hydrogen-storage composites. By means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS) and pressure-composition-temperature (PCT) measurements, the phase structure, microstructure, particle composition and hydriding/dehydriding properties of the composites were studied. Results show that the Mg95Ni5-30%TiFe0.8Mn0.2Zr0.05 composite has the best comprehensive hydriding/dehydridingn properties. It requires only 50 s to absorb its saturated hydrogen capacity of 4.11 wt% at 373 K and desorbs 1.91 wt% and 4.3 wt% hydrogen within 1800 s at 493 K and 523 K, respectively. Moreover, the dehydriding onset temperature of the composite is 420 K, which is 20 K lower than that of Mg95Ni5. The improvement of hydriding/dehydriding properties are related greatly to the structures of the composites, and the addition of TiFe0.8Mn0.2Zr0.05 can improve the dehydriding kinetics of the composites.
Mg95Ni5-x%TiFe0.8Mn0.2Zr0.05 (x = 0, 10, 20, 30) (mass fraction) composites were prepared by hydriding combustion synthesis (HCS) and the products were mechanically milled (MM) to obtain Mg-based hydrogen-storage composites. By means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS) and pressure-composition-temperature (PCT) measurements, the phase structure, microstructure, particle composition and hydriding/dehydriding properties of the composites were studied. Results show that the Mg95Ni5-30%TiFe0.8Mn0.2Zr0.05 composite has the best comprehensive hydriding/dehydridingn properties. It requires only 50 s to absorb its saturated hydrogen capacity of 4.11 wt% at 373 K and desorbs 1.91 wt% and 4.3 wt% hydrogen within 1800 s at 493 K and 523 K, respectively. Moreover, the dehydriding onset temperature of the composite is 420 K, which is 20 K lower than that of Mg95Ni5. The improvement of hydriding/dehydriding properties are related greatly to the structures of the composites, and the addition of TiFe0.8Mn0.2Zr0.05 can improve the dehydriding kinetics of the composites.
2011, 40(9):1658-1661.
Abstract:
Thermal stress simulation and optimization design of the parameters were performed for the W/Cu FGM of divertors by finite element ANSYS code. The results show that the thermal stress is decreased greatly by the introduction of the W/Cu FGM, and the maximum von mises stress is decreased approximately by 58%. The optimal parameters of the FGM are as following: the layer number of FGM is about 5 and the distribution exponential of Cu volume content is about 0.4. Meantime a good heat resistance is shown with a surface temperature below 800 oC under the 10 MW/m2 surface heat load
Thermal stress simulation and optimization design of the parameters were performed for the W/Cu FGM of divertors by finite element ANSYS code. The results show that the thermal stress is decreased greatly by the introduction of the W/Cu FGM, and the maximum von mises stress is decreased approximately by 58%. The optimal parameters of the FGM are as following: the layer number of FGM is about 5 and the distribution exponential of Cu volume content is about 0.4. Meantime a good heat resistance is shown with a surface temperature below 800 oC under the 10 MW/m2 surface heat load
2011, 40(9):1662-1666.
Abstract:
The Mg-0.5%Zn-0.5%Zr-RE alloy was prepared by extrusion and then T5 and T6 heat-treatments were carried out. The tensile mechanical properties were tested. Results indicate that the yield strength of the alloy in T6 state is a little lower than that in T5 state. The tensile strength of the alloy at T6 state is 313 MPa, higher than 289.5 MPa in T5 state. OM observation indicates that the T5 alloy remains the extruded microstructure. TEM results show that the strengthening of Mg-0.5%Zn-0.5%Zr-2.2%Nd-4.0%Y in T6 state originates from the precipitation of β″ and β′ and the interaction of dislocation. The precipitation order of Mg-0.5%Zn-0.5%Zr-2.2%Nd-4.0%Y alloy is SSSS→β″→β′→β under 520 oC, 2 h solution + 200 oC aging
The Mg-0.5%Zn-0.5%Zr-RE alloy was prepared by extrusion and then T5 and T6 heat-treatments were carried out. The tensile mechanical properties were tested. Results indicate that the yield strength of the alloy in T6 state is a little lower than that in T5 state. The tensile strength of the alloy at T6 state is 313 MPa, higher than 289.5 MPa in T5 state. OM observation indicates that the T5 alloy remains the extruded microstructure. TEM results show that the strengthening of Mg-0.5%Zn-0.5%Zr-2.2%Nd-4.0%Y in T6 state originates from the precipitation of β″ and β′ and the interaction of dislocation. The precipitation order of Mg-0.5%Zn-0.5%Zr-2.2%Nd-4.0%Y alloy is SSSS→β″→β′→β under 520 oC, 2 h solution + 200 oC aging
2011, 40(9):1667-1670.
Abstract:
In-situ Mg phase reinforced Mg70Cu17Dy13 bulk metallic glass (BMG) matrix composite with diameter of 3 mm was prepared by a conventional Cu-mold casting method. Mechanical properties and deformation behavior of Mg-Cu-Dy alloys were studied. The results show that the Mg70Cu17Dy13 BMG matrix composite exhibits some work hardening except for initial elastic deformation, and achieves a high fracture compressive strength of 702.38 MPa and a plastic strain of 0.81%. The improvement of the mechanical properties is attributed to the fact that the Mg phase distributed in the amorphous matrix of the alloy has effective load bearing and plastic deformation ability to restrict the expanding of shear bands and cracks and produce its own plastic deformation, which is proved by the shear deforming and fracturing mode and the fracture surfaces characterized by the vein patterns, severe remelting and the very rough and bumpy region of the alloy
In-situ Mg phase reinforced Mg70Cu17Dy13 bulk metallic glass (BMG) matrix composite with diameter of 3 mm was prepared by a conventional Cu-mold casting method. Mechanical properties and deformation behavior of Mg-Cu-Dy alloys were studied. The results show that the Mg70Cu17Dy13 BMG matrix composite exhibits some work hardening except for initial elastic deformation, and achieves a high fracture compressive strength of 702.38 MPa and a plastic strain of 0.81%. The improvement of the mechanical properties is attributed to the fact that the Mg phase distributed in the amorphous matrix of the alloy has effective load bearing and plastic deformation ability to restrict the expanding of shear bands and cracks and produce its own plastic deformation, which is proved by the shear deforming and fracturing mode and the fracture surfaces characterized by the vein patterns, severe remelting and the very rough and bumpy region of the alloy
2011, 40(9):1671-1675.
Abstract:
Aluminum coating on the uranium surface was treated with hot isostatic pressing (HIP). Then the electrochemical corrosion behavior of samples in 50 μL/L Cl- KCl solution were investigated by electrochemical techniques, scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The results indicate that the corrosion-resistant property of the aluminum coating HIPed at 200 oC, 0.5 h, 60 MPa is better than that of the untreated coating, while the corrosion-resistant property is decreased for the coating with HIP at 480 oC, 1.0 h, 60 MPa. The corrosion characteristics of the HIPed aluminum coating is typical local corrosion, and the coating presents cracking and flaking off during corrosion process.
Aluminum coating on the uranium surface was treated with hot isostatic pressing (HIP). Then the electrochemical corrosion behavior of samples in 50 μL/L Cl- KCl solution were investigated by electrochemical techniques, scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The results indicate that the corrosion-resistant property of the aluminum coating HIPed at 200 oC, 0.5 h, 60 MPa is better than that of the untreated coating, while the corrosion-resistant property is decreased for the coating with HIP at 480 oC, 1.0 h, 60 MPa. The corrosion characteristics of the HIPed aluminum coating is typical local corrosion, and the coating presents cracking and flaking off during corrosion process.
2011, 40(9):1676-1679.
Abstract:
The electroreduction of MoCl5 was performed in the binary room temperature ionic liquid, lithium bis[(tri-fluoromethyl) sulfony]amide (LiTFSI) and cesium bis[(tri-fluoromethyl)sulfony]amide (CsTFSI) (eutectic point, 0.07: 0.93 in mole fraction; m.p., 112 oC) at 150 oC for the sake of electrodeposition of molybdenum. Analyses from cyclic voltammetry complemented by SEM-EDAX and XPS show that metallic molybdenum is electrodeposited on nickel substrate in the ionic liquid LiTFSI-CsTFSI containing MoCl5 at 150 oC. Quality of the deposits is improved by using galvanostatic electrolysis and pulsed current electrolysis
The electroreduction of MoCl5 was performed in the binary room temperature ionic liquid, lithium bis[(tri-fluoromethyl) sulfony]amide (LiTFSI) and cesium bis[(tri-fluoromethyl)sulfony]amide (CsTFSI) (eutectic point, 0.07: 0.93 in mole fraction; m.p., 112 oC) at 150 oC for the sake of electrodeposition of molybdenum. Analyses from cyclic voltammetry complemented by SEM-EDAX and XPS show that metallic molybdenum is electrodeposited on nickel substrate in the ionic liquid LiTFSI-CsTFSI containing MoCl5 at 150 oC. Quality of the deposits is improved by using galvanostatic electrolysis and pulsed current electrolysis
2011, 40(9):1680-1682.
Abstract:
Mn1.2Fe0.8P0.76Ge0.24 room temperature magneto-caloric compounds were prepared by mechanical alloying and subsequent spark plasma sintering (SPS) technique. XRD and SEM were used to analyze the phase composition and the microstructure of the sintered bulk samples. Results show that the sintered bulk samples have homogeneous and compact microstructure, but with a little MnO and Fe3Mn4Ge6. DSC curve of the sintered bulk Mn1.2Fe0.8P0.76Ge0.24 compound shows that the Curie temperature TC of the sample is around –10 oC, and at –7 oC the magnetic entropy change is 23 J/(kg·K)
Mn1.2Fe0.8P0.76Ge0.24 room temperature magneto-caloric compounds were prepared by mechanical alloying and subsequent spark plasma sintering (SPS) technique. XRD and SEM were used to analyze the phase composition and the microstructure of the sintered bulk samples. Results show that the sintered bulk samples have homogeneous and compact microstructure, but with a little MnO and Fe3Mn4Ge6. DSC curve of the sintered bulk Mn1.2Fe0.8P0.76Ge0.24 compound shows that the Curie temperature TC of the sample is around –10 oC, and at –7 oC the magnetic entropy change is 23 J/(kg·K)
2011, 40(9):1683-1687.
Abstract:
10%Nb2O5·nH2O-20%Pt/C electrocatalyst for methanol oxidation was prepared by a deposition method, and it was heat treated in Ar atmosphere. The effects of heat treatment on morphology, microstructure and electrochemical performances were characterized by XRD, HRTEM, cyclic voltammetry and chronoamperograms. The results show that with the increase of heat-treatment temperature, the size of Pt particles is increased, and the catalytic performance becomes higher. In comparison with the 20%Pt/C without heat treatment, the catalytic performance of 10%Nb2O5·nH2O-20%Pt/C with heat treatment at 700 oC for methanol oxidation is best. Its initial potential of methanol oxidation is reduced by 150 mV, and the peak current for methanol oxidation is increased by 2.48 times
10%Nb2O5·nH2O-20%Pt/C electrocatalyst for methanol oxidation was prepared by a deposition method, and it was heat treated in Ar atmosphere. The effects of heat treatment on morphology, microstructure and electrochemical performances were characterized by XRD, HRTEM, cyclic voltammetry and chronoamperograms. The results show that with the increase of heat-treatment temperature, the size of Pt particles is increased, and the catalytic performance becomes higher. In comparison with the 20%Pt/C without heat treatment, the catalytic performance of 10%Nb2O5·nH2O-20%Pt/C with heat treatment at 700 oC for methanol oxidation is best. Its initial potential of methanol oxidation is reduced by 150 mV, and the peak current for methanol oxidation is increased by 2.48 times
Wang Jianzhong
,
Xi Zhengping
,
Tang Huiping
,
Huang Weidong
,
Zhu Jilei
,
Li Cheng
,
Ao Qingbo
,
Zhi Hao
2011, 40(9):1688-1692.
Abstract:
The present paper describes briefly the harm of electromagnetic radiation and the mechanism of electromagnetic shielding material and it focuses on the application and research progress of electromagnetic shielding fabric, electromagnetic shielding polymer and electromagnetic shielding architecture and decoration material made by metal fiber and predicts the development of electromagnetic shielding material in the future. It points out that great attention should be paid to developing an advanced, high-property, low-consumption and green-environment-protection electromagnetic shielding materials with high absorption and low reflection and transmission. Furthermore, it considers that the internal composition and structure need optimizing and the forming process needs improving in order to enhance shielding effectiveness
The present paper describes briefly the harm of electromagnetic radiation and the mechanism of electromagnetic shielding material and it focuses on the application and research progress of electromagnetic shielding fabric, electromagnetic shielding polymer and electromagnetic shielding architecture and decoration material made by metal fiber and predicts the development of electromagnetic shielding material in the future. It points out that great attention should be paid to developing an advanced, high-property, low-consumption and green-environment-protection electromagnetic shielding materials with high absorption and low reflection and transmission. Furthermore, it considers that the internal composition and structure need optimizing and the forming process needs improving in order to enhance shielding effectiveness
