Volume 38,Issue 1,2009 Table of Contents
2009, 38(1):7-10.
Abstract:
Effect of Nd on as-cast microstructure and mechanical properties of AZ31 magnesium alloy were investigated by ICP, metallographic microscopy, SEM, EDS, XRD and mechanical measurement. The results show that the microcontent of Nd added in AZ31 alloy could result in the formation of intermetallic compounds of Al2Nd and Mg12Nd at grain boundary and in α-Mg matrix, and the absorption rate of Nd reached 95%, which obviously refined AZ31 alloy microstructure and further improved mechanical properties. The AZ31 alloy containing Nd showed a tensile strength of 245 MPa, a yield strength of 171 MPa and a elongation of 9%.
Effect of Nd on as-cast microstructure and mechanical properties of AZ31 magnesium alloy were investigated by ICP, metallographic microscopy, SEM, EDS, XRD and mechanical measurement. The results show that the microcontent of Nd added in AZ31 alloy could result in the formation of intermetallic compounds of Al2Nd and Mg12Nd at grain boundary and in α-Mg matrix, and the absorption rate of Nd reached 95%, which obviously refined AZ31 alloy microstructure and further improved mechanical properties. The AZ31 alloy containing Nd showed a tensile strength of 245 MPa, a yield strength of 171 MPa and a elongation of 9%.
2009, 38(1):11-14.
Abstract:
In order to improve the performances of electrode materials for super-capacitors, multi-element composite electrodes were prepared using RuO2 and MnO2 as active materials，and active carbon as basic materials. Good electrochemical performances of the composite electrodes were confirmed by cyclic voltammetry, galvano static charge/discharge and ac impedance measurements. When the content of MnO2 is 20wt% in composite electrode materials, the specific capacitance of MnO2/AC composite electrodes can reach 128 F/g with a resistance of 2.62 Ω. When the contents of RuO2 and MnO2 are separately 20wt% in composite electrode materials, the specific capacitance of RuO2/MnO2/AC composite electrodes can reach 266 F/g with a resistance of 0.86 Ω almost without any change of capacitance during 1500 cycles of charge/discharge. It is indicated that the multi-factor composite electrodes with RuO2/ MnO2 / AC are ideal electrode materials for super-capacitors.
In order to improve the performances of electrode materials for super-capacitors, multi-element composite electrodes were prepared using RuO2 and MnO2 as active materials，and active carbon as basic materials. Good electrochemical performances of the composite electrodes were confirmed by cyclic voltammetry, galvano static charge/discharge and ac impedance measurements. When the content of MnO2 is 20wt% in composite electrode materials, the specific capacitance of MnO2/AC composite electrodes can reach 128 F/g with a resistance of 2.62 Ω. When the contents of RuO2 and MnO2 are separately 20wt% in composite electrode materials, the specific capacitance of RuO2/MnO2/AC composite electrodes can reach 266 F/g with a resistance of 0.86 Ω almost without any change of capacitance during 1500 cycles of charge/discharge. It is indicated that the multi-factor composite electrodes with RuO2/ MnO2 / AC are ideal electrode materials for super-capacitors.
2009, 38(1):15-18.
Abstract:
Vanadium-based hydrogen storage alloys are easily corroded in KOH solution, which leads to their poor electrochemical cyclic durability in alkaline solution and limits their application in the Ni/MH battery. In this paper, the structure transformation of V3TiNi0.56Mx alloys during full immersion corrosion in alkaline solution was investigated; the corrosion potentials, the Tafel curves and the impedance spectra were tested for the V3TiNi0.56Mx alloys in alkaline solution. The results show that the corrosion of V3TiNi0.56Mx alloys in alkaline solution is caused by the continuous dissolve of the TiNi compound based phase as a micro-current collector, and the addition of alloy elements Cr and Al can prevent the dissolve of TiNi compound based phase, shift the alloy corrosion potential and improve the corrosion resistance of alloys in alkaline solution.
Vanadium-based hydrogen storage alloys are easily corroded in KOH solution, which leads to their poor electrochemical cyclic durability in alkaline solution and limits their application in the Ni/MH battery. In this paper, the structure transformation of V3TiNi0.56Mx alloys during full immersion corrosion in alkaline solution was investigated; the corrosion potentials, the Tafel curves and the impedance spectra were tested for the V3TiNi0.56Mx alloys in alkaline solution. The results show that the corrosion of V3TiNi0.56Mx alloys in alkaline solution is caused by the continuous dissolve of the TiNi compound based phase as a micro-current collector, and the addition of alloy elements Cr and Al can prevent the dissolve of TiNi compound based phase, shift the alloy corrosion potential and improve the corrosion resistance of alloys in alkaline solution.
2009, 38(1):19-24.
Abstract:
The effect of the deformation temperature, deformation degree, strain rate and their interaction on the microstructure and mechanical properties in the high temperature deformation of Ti-6Al-4V alloy was investigated. The experimental results show that the deformation degree and strain rate have significant influence on the microstructure and mechanical properties, in which finer microstructure and higher tensile strength can be obtained at a middle deformation degree and a higher strain rate. The interactions between the deformation temperature and the deformation degree or the strain rate in the high temperature deformation of Ti-6Al-4V alloy are significant, especially being deformed at the temperature just under the β transus, the ductility and tensile strength are sensitive to all of processing parameters including their interactions. So the interactions should be considered to optimize the processing parameters in order to meet the requirements of the mechanical properties.
The effect of the deformation temperature, deformation degree, strain rate and their interaction on the microstructure and mechanical properties in the high temperature deformation of Ti-6Al-4V alloy was investigated. The experimental results show that the deformation degree and strain rate have significant influence on the microstructure and mechanical properties, in which finer microstructure and higher tensile strength can be obtained at a middle deformation degree and a higher strain rate. The interactions between the deformation temperature and the deformation degree or the strain rate in the high temperature deformation of Ti-6Al-4V alloy are significant, especially being deformed at the temperature just under the β transus, the ductility and tensile strength are sensitive to all of processing parameters including their interactions. So the interactions should be considered to optimize the processing parameters in order to meet the requirements of the mechanical properties.
2009, 38(1):25-28.
Abstract:
Cooling rate has drastic effects on the continuous cooling transformation of Ti-45Al-5Nb and Ti-45Al-5Nb-0.3Y alloys. Furnace cooling (FC) leads to the fully lamellar microstructure. Air cooling suppresses the lamellar transformation by the α→γm reaction. Oil cooling leads to the extremely fine lamellar microstructure. At a higher cooling rate (such as water cooling), the α2 phases are predominant. By air cooling a feathery structure disappears and the α2 phase increases. By water cooling, the extremely fine lamellar regions located at initial α2 grain boundaries are smaller and increase for the Ti-45Al-5Nb-0.3Y alloy. Y addition has slight effect on the phase transformation of Ti-45Al-Nb alloy.
Cooling rate has drastic effects on the continuous cooling transformation of Ti-45Al-5Nb and Ti-45Al-5Nb-0.3Y alloys. Furnace cooling (FC) leads to the fully lamellar microstructure. Air cooling suppresses the lamellar transformation by the α→γm reaction. Oil cooling leads to the extremely fine lamellar microstructure. At a higher cooling rate (such as water cooling), the α2 phases are predominant. By air cooling a feathery structure disappears and the α2 phase increases. By water cooling, the extremely fine lamellar regions located at initial α2 grain boundaries are smaller and increase for the Ti-45Al-5Nb-0.3Y alloy. Y addition has slight effect on the phase transformation of Ti-45Al-Nb alloy.
2009, 38(1):29-33.
Abstract:
In order to control the morphologies of TiO2 nanotube arrays, it is significant to investigate the effects of anodization parameters on the formation process and the microstructure of nanotube arrays. Titanium (99.6%) was anodized in 0.1 ~ 1.0 wt% HF solutions by using Pt as cathode in this work. Anodization process was carried out at voltage range from 0.4 V to 14.5 V and solution temperature from 5 ℃ to 40 ℃. The linear sweep anodic polarization curve and current density-time curves were obtained by means of electrochemical workstation. The morphology of the oxide films was observed with SEM. The effects of time, anodizing voltage, solution temperature on the formation process and the microstructure of titania arrays were studied, respectively. The results show that the growth rate, the nano-pore diameter and the thickness of titania film are obviously affected by anodic oxidation condition, which increased with increasing voltage. But the higher, the voltage, the longer, the time, to achieve balanced growth. It is also found that a higher solution temperature or a higher HF concentration is beneficial to improve the growth rate, shorten the time to equilibrium and reduce the steady nanotube length at equilibrium stage.
In order to control the morphologies of TiO2 nanotube arrays, it is significant to investigate the effects of anodization parameters on the formation process and the microstructure of nanotube arrays. Titanium (99.6%) was anodized in 0.1 ~ 1.0 wt% HF solutions by using Pt as cathode in this work. Anodization process was carried out at voltage range from 0.4 V to 14.5 V and solution temperature from 5 ℃ to 40 ℃. The linear sweep anodic polarization curve and current density-time curves were obtained by means of electrochemical workstation. The morphology of the oxide films was observed with SEM. The effects of time, anodizing voltage, solution temperature on the formation process and the microstructure of titania arrays were studied, respectively. The results show that the growth rate, the nano-pore diameter and the thickness of titania film are obviously affected by anodic oxidation condition, which increased with increasing voltage. But the higher, the voltage, the longer, the time, to achieve balanced growth. It is also found that a higher solution temperature or a higher HF concentration is beneficial to improve the growth rate, shorten the time to equilibrium and reduce the steady nanotube length at equilibrium stage.
2009, 38(1):34-37.
Abstract:
Dynamic shearing experiment has been done for TC6 titanium alloy by using the technology of split Hopkinson bar. The formation mechanics of adiabatic shear band of TC6 titanium alloy have been studied by optical microscope (OP), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is shown that the formation mechanics of adiabatic shear band are different due to the different microstructures for the TC6 titanium alloy. To the spherical equiaxed microstructures, its formation of shear band is due to the multiplication, moving and clogging of dislocation; and to the lamellar microstructures, the formation of shear band is due to the dynamic recrystallization.
Dynamic shearing experiment has been done for TC6 titanium alloy by using the technology of split Hopkinson bar. The formation mechanics of adiabatic shear band of TC6 titanium alloy have been studied by optical microscope (OP), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is shown that the formation mechanics of adiabatic shear band are different due to the different microstructures for the TC6 titanium alloy. To the spherical equiaxed microstructures, its formation of shear band is due to the multiplication, moving and clogging of dislocation; and to the lamellar microstructures, the formation of shear band is due to the dynamic recrystallization.
2009, 38(1):38-41.
Abstract:
The microdefects and free electron densities in B2, R and B19’ phases of Ni50.78Ti49.22 alloy have been studied by positron lifetime measurements. Comparing the lifetime parameters of the Ni50.78Ti49.22 alloy measured at 285 and 227 K, it is found that the free electron density of the R phase is lower than that of the B2 phase; the open volume of the defects for the R phase is larger, while the concentration of these defects is lower than that of the B2 phase. The Ni50.78Ti49.22 alloy is the B19’ phase at 100 K. In comparison with the R phase, the free electron density of the B19’ phase increases, the open volume of defects for the B19’ phase decreases, and the concentration of these defects increases. It is found that the microdefects and the free electron density play important roles during the multi-step transformations (B2→R→B19’) for the Ni50.78Ti49.22 alloy with the temperature decreasing.
The microdefects and free electron densities in B2, R and B19’ phases of Ni50.78Ti49.22 alloy have been studied by positron lifetime measurements. Comparing the lifetime parameters of the Ni50.78Ti49.22 alloy measured at 285 and 227 K, it is found that the free electron density of the R phase is lower than that of the B2 phase; the open volume of the defects for the R phase is larger, while the concentration of these defects is lower than that of the B2 phase. The Ni50.78Ti49.22 alloy is the B19’ phase at 100 K. In comparison with the R phase, the free electron density of the B19’ phase increases, the open volume of defects for the B19’ phase decreases, and the concentration of these defects increases. It is found that the microdefects and the free electron density play important roles during the multi-step transformations (B2→R→B19’) for the Ni50.78Ti49.22 alloy with the temperature decreasing.
2009, 38(1):42-45.
Abstract:
The grain boundary segregation behavior of Ti14, a new typical α+Ti2Cu alloy, was investigated after semi-solid forging at different temperatures. The results reveal that Cu is segregated in grain boundary during semi-solid deformation and precipitated as Ti2Cu phase during the solidification. Temperature has effects on the microstructures of precipitates. A nucleation and precipitation model of Ti2Cu was raised to express the processing of nucleation and precipitation, which can be explained by a nonclassical nucleation and growth theory.
The grain boundary segregation behavior of Ti14, a new typical α+Ti2Cu alloy, was investigated after semi-solid forging at different temperatures. The results reveal that Cu is segregated in grain boundary during semi-solid deformation and precipitated as Ti2Cu phase during the solidification. Temperature has effects on the microstructures of precipitates. A nucleation and precipitation model of Ti2Cu was raised to express the processing of nucleation and precipitation, which can be explained by a nonclassical nucleation and growth theory.
2009, 38(1):46-49.
Abstract:
Hot Deformation Behavior of Ti-1300 Alloy
Hot Deformation Behavior of Ti-1300 Alloy
2009, 38(1):50-53.
Abstract:
The phase compositions of hydrided TiCr1.8-xVx hydrogen storage alloys were examined by X-ray diffraction (XRD) and thermal gravity-differential scanning calorimetry-mass spectrometry (TG-DSC-MS) firstly to study the dependence of hydrogen desorption characteristics with temperature, and the states of released hydrogen were inspected by the mass spectrometry. The active energy of hydrogen desorption was calculated at different heating rates by the differential scanning calorimetry tests.
The phase compositions of hydrided TiCr1.8-xVx hydrogen storage alloys were examined by X-ray diffraction (XRD) and thermal gravity-differential scanning calorimetry-mass spectrometry (TG-DSC-MS) firstly to study the dependence of hydrogen desorption characteristics with temperature, and the states of released hydrogen were inspected by the mass spectrometry. The active energy of hydrogen desorption was calculated at different heating rates by the differential scanning calorimetry tests.
2009, 38(1):54-58.
Abstract:
In present work, a new type of bulk metallic glass quaternary alloy, Zr51Al9.96Ni14.34Cu24.7, was designed by using binary eutectic clusters method. The new alloy displays a high strength up to 2356 MPa and a large plastic strain of 14.6% at room temperature according to compression test. The excellent ductility of the present glassy alloy is attributed to the deformation to induce the nanocrystalline, which can induce the formation of numerous new shear bands and enhance the density of shear bands; on the other hand, to influence the propagation of shear bands to intersect and to branch during deformation process, as a result, the plasticity of alloy is improved.
In present work, a new type of bulk metallic glass quaternary alloy, Zr51Al9.96Ni14.34Cu24.7, was designed by using binary eutectic clusters method. The new alloy displays a high strength up to 2356 MPa and a large plastic strain of 14.6% at room temperature according to compression test. The excellent ductility of the present glassy alloy is attributed to the deformation to induce the nanocrystalline, which can induce the formation of numerous new shear bands and enhance the density of shear bands; on the other hand, to influence the propagation of shear bands to intersect and to branch during deformation process, as a result, the plasticity of alloy is improved.
2009, 38(1):59-63.
Abstract:
The effects of cycle temperatures on the thermal fatigue crack growth of three kinds of superalloys were investigated. The experimental results show that the crack growth rate increases with the rise of cycle temperature. Optical Microscopy (OM) and Scanning electron microscopy (SEM) observations reveal that multiple small cracks primarily initiated at the notch tip in any temperature range. Subsequently, only one or two small cracks can continue to grow, and finally form the main cracks. The crack growth behavior varies distinctly for different alloys. In general, thermal fatigue cracks propagate along a preferential direction with the dendrite growth direction in single crystal superalloy, but along the interdendritic region for the Mar-M002 alloy.
The effects of cycle temperatures on the thermal fatigue crack growth of three kinds of superalloys were investigated. The experimental results show that the crack growth rate increases with the rise of cycle temperature. Optical Microscopy (OM) and Scanning electron microscopy (SEM) observations reveal that multiple small cracks primarily initiated at the notch tip in any temperature range. Subsequently, only one or two small cracks can continue to grow, and finally form the main cracks. The crack growth behavior varies distinctly for different alloys. In general, thermal fatigue cracks propagate along a preferential direction with the dendrite growth direction in single crystal superalloy, but along the interdendritic region for the Mar-M002 alloy.
2009, 38(1):64-67.
Abstract:
The microstructure of γ′ phase in HIPFGH95 superalloy was investigated by use of SEM and TEM. The results show that the microstructure is a mixture of recrystal grains and original dendrite crystals after the heat treatment. The undissolved particles of γ′ phase during the solution treatment distribute in the grain boundaries. Meanwhile, there are three different sizes of γ′ particles within the recrystal grains. Among them, the big and square γ′ particles exhibit arrays of every 8 particles, which are formed from the spitted single γ′ particles precipitated during the cooling procedure from 1160 ℃. Moreover, which would decompose to form finer γ′ precipitates, at the same time, the cube γ′ particles disappear with the growth of finer γ′ precipitates.
The microstructure of γ′ phase in HIPFGH95 superalloy was investigated by use of SEM and TEM. The results show that the microstructure is a mixture of recrystal grains and original dendrite crystals after the heat treatment. The undissolved particles of γ′ phase during the solution treatment distribute in the grain boundaries. Meanwhile, there are three different sizes of γ′ particles within the recrystal grains. Among them, the big and square γ′ particles exhibit arrays of every 8 particles, which are formed from the spitted single γ′ particles precipitated during the cooling procedure from 1160 ℃. Moreover, which would decompose to form finer γ′ precipitates, at the same time, the cube γ′ particles disappear with the growth of finer γ′ precipitates.
2009, 38(1):68-71.
Abstract:
The stress impedance effect is studied for the Co66Fe4Cr2Si12B16 amorphous ribbons under bending strain. One of the amorphous ribbons is in as-cast state and the other is treated by pulse current, and the both amorphous ribbons are of the negative magnetostriction. The experimental result shows that the amplitude ratio of the output voltage from the two ends is larger than 40% for the pulse current annealed amorphous ribbon of 50 mm in length only under a bending strain of 5 mm deflection. The stress impedance sensitivity can be improved by the pulse current annealing at 35 A/mm2 and 2 Hz for 30 s. The bending impedance increases with the applied compressive stress, and decreases with the tensile stress, and can be used to develop a new force sensor with large gauge factor and some novel smart materials.
The stress impedance effect is studied for the Co66Fe4Cr2Si12B16 amorphous ribbons under bending strain. One of the amorphous ribbons is in as-cast state and the other is treated by pulse current, and the both amorphous ribbons are of the negative magnetostriction. The experimental result shows that the amplitude ratio of the output voltage from the two ends is larger than 40% for the pulse current annealed amorphous ribbon of 50 mm in length only under a bending strain of 5 mm deflection. The stress impedance sensitivity can be improved by the pulse current annealing at 35 A/mm2 and 2 Hz for 30 s. The bending impedance increases with the applied compressive stress, and decreases with the tensile stress, and can be used to develop a new force sensor with large gauge factor and some novel smart materials.
2009, 38(1):72-75.
Abstract:
The microstructure and magnetic properties of the Tb0.3Dy0.7(Fe1-xPtx)1.95 (x=0.00, 0.02, 0.04, 0.06, 0.08) alloys were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and resistance strain gauge techniques. It is found that the alloys are the single phase microstructure of MgCu2 cubic Laves when the Pt content is less than 0.06 at%, with a line increase of the lattice parameters with the increase of Pt content. But the magnetostriction coefficients decrease with the increase of Pt content, and increase with the increase of external magnetic fields. When the alloys were heated for 4 h at 950 ℃, a better magnetostriction effect is obtained. A small amount of RFe3 phase exists when the Pt content is 0.08 at%.
The microstructure and magnetic properties of the Tb0.3Dy0.7(Fe1-xPtx)1.95 (x=0.00, 0.02, 0.04, 0.06, 0.08) alloys were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and resistance strain gauge techniques. It is found that the alloys are the single phase microstructure of MgCu2 cubic Laves when the Pt content is less than 0.06 at%, with a line increase of the lattice parameters with the increase of Pt content. But the magnetostriction coefficients decrease with the increase of Pt content, and increase with the increase of external magnetic fields. When the alloys were heated for 4 h at 950 ℃, a better magnetostriction effect is obtained. A small amount of RFe3 phase exists when the Pt content is 0.08 at%.
2009, 38(1):76-79.
Abstract:
The mechanical properties of the thick Ni foam prepared by electrodeposition technology are not homogeneous from the surface to the middle section due to the different Ni deposit thicknesses on the ligament of PU foam, resulting in a larger deposition thickness ratio (DTR). In this study, the effects of the constitution of electrolyte and the current density during electrodepositing process on the DTR of thick Ni foam were investigated. The results show that the current density has the predominant effects; and the conductivity of electrolyte and the concentration of main salt are also the important factors.
The mechanical properties of the thick Ni foam prepared by electrodeposition technology are not homogeneous from the surface to the middle section due to the different Ni deposit thicknesses on the ligament of PU foam, resulting in a larger deposition thickness ratio (DTR). In this study, the effects of the constitution of electrolyte and the current density during electrodepositing process on the DTR of thick Ni foam were investigated. The results show that the current density has the predominant effects; and the conductivity of electrolyte and the concentration of main salt are also the important factors.
2009, 38(1):80-85.
Abstract:
NbCr2 alloys of Laves phase were prepared by mechanical alloying and hot pressing, and the influences of Al on the microstructure and mechanical properties, especially fracture toughness, of NbCr2 alloys were studied. The results show that the alloying element Al mainly exists in the Cr site in the NbCr2 Laves phase. The hardness of NbCr2 alloys increases slightly with the increase of Al adding amount, but no obvious effect on the fracture toughness for the NbCr2 alloys. At a higher Al adding level (i. e. 12 at%), the fracture toughness of the NbCr2 alloy is 6.8 MPa, a higher value than that of the cast alloys (1.2 MPa m1/2)
NbCr2 alloys of Laves phase were prepared by mechanical alloying and hot pressing, and the influences of Al on the microstructure and mechanical properties, especially fracture toughness, of NbCr2 alloys were studied. The results show that the alloying element Al mainly exists in the Cr site in the NbCr2 Laves phase. The hardness of NbCr2 alloys increases slightly with the increase of Al adding amount, but no obvious effect on the fracture toughness for the NbCr2 alloys. At a higher Al adding level (i. e. 12 at%), the fracture toughness of the NbCr2 alloy is 6.8 MPa, a higher value than that of the cast alloys (1.2 MPa m1/2)
2009, 38(1):86-89.
Abstract:
Based on the microscopic phase-field dynamic diffusion equation (the Langevin equation), the effects of concentration and temperature on the antisite defect evolution in Al3Li phase are investigated. The results show that the main antisite defect in Al3Li phase is AlLi, in which the Li sites are taken by Al atoms; there also exists a little amount of LiAl, in which the Al sites are taken by Li atoms. The two antisite defects are all increase with the increase of temperature, and the rising rate for AlLi is far larger than for LiAl. With the increase of Li concentration, the AlLi concentration decreases slowly and the LiAl concentration increases slightly, but still far less than the AlLi concentration . It is found that the effects of temperature on the antisite defects are more obvious than the concentration.
Based on the microscopic phase-field dynamic diffusion equation (the Langevin equation), the effects of concentration and temperature on the antisite defect evolution in Al3Li phase are investigated. The results show that the main antisite defect in Al3Li phase is AlLi, in which the Li sites are taken by Al atoms; there also exists a little amount of LiAl, in which the Al sites are taken by Li atoms. The two antisite defects are all increase with the increase of temperature, and the rising rate for AlLi is far larger than for LiAl. With the increase of Li concentration, the AlLi concentration decreases slowly and the LiAl concentration increases slightly, but still far less than the AlLi concentration . It is found that the effects of temperature on the antisite defects are more obvious than the concentration.
2009, 38(1):90-94.
Abstract:
The effects of the Cr substitutional behavior in the different third and fourth nearest interactive potential is studied by the phase field method in Ni75Al15Cr10 at temperature 873 K. The results show: the evolution of the Cr long range order parameter demonstrates the existence of Cr’s substitution for both Ni and Al sites in L12 type ordered structure, and whose solubility in γ′ phase is opposite between the third and fourth shell potential. Besides that, with the increase of the Ni-Al, Ni-Cr third nearest pairwise potential, the occupation of Cr at α sublattice sites enhance while β site’s occupation falls down, but for the Ni-Al, Ni-Cr third nearest pairwise potential, this tendency reverse. As the Al-Cr third pairwise potential increase, the Cr occupation at α and β sites increase. Otherwise the increase of the Al-Cr fourth nearest pairwise potential promotes Cr’s substitution for the Ni sites and decrease Cr’s substitution for Al sites.
The effects of the Cr substitutional behavior in the different third and fourth nearest interactive potential is studied by the phase field method in Ni75Al15Cr10 at temperature 873 K. The results show: the evolution of the Cr long range order parameter demonstrates the existence of Cr’s substitution for both Ni and Al sites in L12 type ordered structure, and whose solubility in γ′ phase is opposite between the third and fourth shell potential. Besides that, with the increase of the Ni-Al, Ni-Cr third nearest pairwise potential, the occupation of Cr at α sublattice sites enhance while β site’s occupation falls down, but for the Ni-Al, Ni-Cr third nearest pairwise potential, this tendency reverse. As the Al-Cr third pairwise potential increase, the Cr occupation at α and β sites increase. Otherwise the increase of the Al-Cr fourth nearest pairwise potential promotes Cr’s substitution for the Ni sites and decrease Cr’s substitution for Al sites.
2009, 38(1):95-98.
Abstract:
The compact tension (CT) specimens of beryllium were employed to study the fracture behavior and mechanical properties. The local stress distribution near a notch in CT beryllium was measured by combination of an X-ray stress analysis and a custom-designed load device, and the fracture morphology was observed by SEM. The results show that the local stress near notch tip is much higher than that in other areas, and a cracking occurs firstly in this area. The loading-cracking displacement curve of the CT Be was obtained, and the fracture toughness value was calculated from the curve. The CT specimen fracture surfaces mainly exhibit a cleave morphology with three typical areas. Some open micro-cracks along the basal slip plane were formed in the crack tip, and its growth was controlled by primary stress after reaching a critical length. The tensile strength was evaluated by the fracture toughness theory when a crack existed in the Be material.
The compact tension (CT) specimens of beryllium were employed to study the fracture behavior and mechanical properties. The local stress distribution near a notch in CT beryllium was measured by combination of an X-ray stress analysis and a custom-designed load device, and the fracture morphology was observed by SEM. The results show that the local stress near notch tip is much higher than that in other areas, and a cracking occurs firstly in this area. The loading-cracking displacement curve of the CT Be was obtained, and the fracture toughness value was calculated from the curve. The CT specimen fracture surfaces mainly exhibit a cleave morphology with three typical areas. Some open micro-cracks along the basal slip plane were formed in the crack tip, and its growth was controlled by primary stress after reaching a critical length. The tensile strength was evaluated by the fracture toughness theory when a crack existed in the Be material.
2009, 38(1):99-103.
Abstract:
The AZ31B magnesium alloy coated with calcium phosphate (CA-P/AZ31B) was implanted in rabbit skeletal and muscular tissue in this study. The inflammatory reaction in skeletal and muscular tissue was observed around the magnesium alloy in vivo. The microstructure and cytotoxic effect of the magnesium alloy were detected. The results show that the release and degradation process of AZ31B magnesium alloy was efficiently delayed by coated with CA-P. The surface roughness of AZ31B magnesium alloy was raised by coated with CA-P, whereas the inflammation induced by AZ31B magnesium alloy was inhibited in vivo. By hemolysis tests, the hemolytic effect was significantly decreased for the CA-P/AZ31B magnesium alloy coated with CA-P. Therefore, the alloy would be a new generation of degradable and biocompatible materials for medical applications.
The AZ31B magnesium alloy coated with calcium phosphate (CA-P/AZ31B) was implanted in rabbit skeletal and muscular tissue in this study. The inflammatory reaction in skeletal and muscular tissue was observed around the magnesium alloy in vivo. The microstructure and cytotoxic effect of the magnesium alloy were detected. The results show that the release and degradation process of AZ31B magnesium alloy was efficiently delayed by coated with CA-P. The surface roughness of AZ31B magnesium alloy was raised by coated with CA-P, whereas the inflammation induced by AZ31B magnesium alloy was inhibited in vivo. By hemolysis tests, the hemolytic effect was significantly decreased for the CA-P/AZ31B magnesium alloy coated with CA-P. Therefore, the alloy would be a new generation of degradable and biocompatible materials for medical applications.
2009, 38(1):104-109.
Abstract:
The dynamic precipitation of the β phase in AZ91 magnesium alloy during extrusion process and its effects on the microstructures and tensile properties of the alloy are studied. It is found that the mechanical properties are effectively improved by the extrusion process and the dynamic precipitation of the β phase occurs during the extrusion process. The characteristics of precipitation are influenced by the extrusion temperature and extrusion ratio. The dynamically precipitated β phase has a limited direct effect on the tensile properties. The effects of β phase on the tensile properties come from its influence on the microstructure evolution through the dynamic crystallization. The authors consider that the mechanical properties of AZ91 can be further improved by controlling the working processes to optimize the precipitation characteristics of the β phase.
The dynamic precipitation of the β phase in AZ91 magnesium alloy during extrusion process and its effects on the microstructures and tensile properties of the alloy are studied. It is found that the mechanical properties are effectively improved by the extrusion process and the dynamic precipitation of the β phase occurs during the extrusion process. The characteristics of precipitation are influenced by the extrusion temperature and extrusion ratio. The dynamically precipitated β phase has a limited direct effect on the tensile properties. The effects of β phase on the tensile properties come from its influence on the microstructure evolution through the dynamic crystallization. The authors consider that the mechanical properties of AZ91 can be further improved by controlling the working processes to optimize the precipitation characteristics of the β phase.
2009, 38(1):110-114.
Abstract:
The corrosion behavior of bulk amorphous Mg65Cu25Gd10 alloy was studied by electrochemical measurement. The potentiodynamic polarization tests were carried out in 0.01 mol/L NaCl solution and 0.1 mol/L NaOH solution with pH=13. The amorphous Mg65Cu25Gd10 alloy was spontaneously passivated at a significantly low passivation current density in the two kinds of solutions. The surface morphology and corrosive products of samples after dipping tests were characterized by scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). The potentiostatically formed surface layers on Mg65Cu25Gd10 were investigated with a depth profile X-ray photoelectron spectroscopy (DP-XPS). The results show that the potentiostatically formed surface layer in NaOH solution is more compact and less porous than that in NaCl solution, indicating that the Mg65Cu25Gd10 alloy has a better corrosion resistance in the solution without Cl－.
The corrosion behavior of bulk amorphous Mg65Cu25Gd10 alloy was studied by electrochemical measurement. The potentiodynamic polarization tests were carried out in 0.01 mol/L NaCl solution and 0.1 mol/L NaOH solution with pH=13. The amorphous Mg65Cu25Gd10 alloy was spontaneously passivated at a significantly low passivation current density in the two kinds of solutions. The surface morphology and corrosive products of samples after dipping tests were characterized by scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). The potentiostatically formed surface layers on Mg65Cu25Gd10 were investigated with a depth profile X-ray photoelectron spectroscopy (DP-XPS). The results show that the potentiostatically formed surface layer in NaOH solution is more compact and less porous than that in NaCl solution, indicating that the Mg65Cu25Gd10 alloy has a better corrosion resistance in the solution without Cl－.
2009, 38(1):115-119.
Abstract:
The equilibrium geometries, the electronic structures, the vibration properties and the bond properties of the tier-like structures of Mg2B6, Mg4B10, Mg6B13 and Mg8B16 clusters have been studied by the hybrid density functional B3LYP on the 6-31G* level. The calculated results show that the bond lengths are about 0.225~0.235 nm for Mg-B and 0.154~0.191 nm for B-B; the natural charge of B atoms is about –0.29~–1.10 e by population analysis and about +1.24~+1.45 e for Mg atoms; and the dynamic stabilities of Mg4B10 clusters are higher than that of other clusters.
The equilibrium geometries, the electronic structures, the vibration properties and the bond properties of the tier-like structures of Mg2B6, Mg4B10, Mg6B13 and Mg8B16 clusters have been studied by the hybrid density functional B3LYP on the 6-31G* level. The calculated results show that the bond lengths are about 0.225~0.235 nm for Mg-B and 0.154~0.191 nm for B-B; the natural charge of B atoms is about –0.29~–1.10 e by population analysis and about +1.24~+1.45 e for Mg atoms; and the dynamic stabilities of Mg4B10 clusters are higher than that of other clusters.
2009, 38(1):120-125.
Abstract:
The valence electron structures of Al2Ca and Mg2Ca, and the interface electron structures of Al2Ca(111)//α-Mg(), Mg2Ca(001)//α-Mg(0001) are calculated and analyzed based on the empirical electron theory of solids and molecules and an improved Thomas-Fermi-Dirac(TFD) theory. The strongest bond (nA=0.397 06) of Al2Ca and the secondary strong bond (nA=0.302 45) of Mg2Ca greatly hinder the dislocation movement and grain-boundary sliding, so that the alloy’s intensity is enhanced. Compared the FV value of γ-Mg17Al12 (＝44.22), the total bond-forming ability in unit volumevalue of Al2Ca and Mg2Ca is 99.25 and 47.66, respectively. It shows that the high temperature stability of Al2Ca is better and its existence is advantageous to improve the high temperature performance of Mg-Al alloy. The interface electronic density difference of the second phase in crystal boundary and the substrate is greater than that of the γ-Mg17Al12(110)//α-Mg(0001), the γ-Mg17Al12 and the substrate, with a better interface strengthening effect effectively to increase the operation temperature of Mg-Al alloy. The bigger difference of the interface electron densities would prevent grain growth and a finer microstructure can be obtained during solidification, as a result, the nucleation rate of γ-Mg17Al12 is increased and the mechanics properties of Mg-Al alloy are enhanced.
The valence electron structures of Al2Ca and Mg2Ca, and the interface electron structures of Al2Ca(111)//α-Mg(), Mg2Ca(001)//α-Mg(0001) are calculated and analyzed based on the empirical electron theory of solids and molecules and an improved Thomas-Fermi-Dirac(TFD) theory. The strongest bond (nA=0.397 06) of Al2Ca and the secondary strong bond (nA=0.302 45) of Mg2Ca greatly hinder the dislocation movement and grain-boundary sliding, so that the alloy’s intensity is enhanced. Compared the FV value of γ-Mg17Al12 (＝44.22), the total bond-forming ability in unit volumevalue of Al2Ca and Mg2Ca is 99.25 and 47.66, respectively. It shows that the high temperature stability of Al2Ca is better and its existence is advantageous to improve the high temperature performance of Mg-Al alloy. The interface electronic density difference of the second phase in crystal boundary and the substrate is greater than that of the γ-Mg17Al12(110)//α-Mg(0001), the γ-Mg17Al12 and the substrate, with a better interface strengthening effect effectively to increase the operation temperature of Mg-Al alloy. The bigger difference of the interface electron densities would prevent grain growth and a finer microstructure can be obtained during solidification, as a result, the nucleation rate of γ-Mg17Al12 is increased and the mechanics properties of Mg-Al alloy are enhanced.
2009, 38(1):126-130.
Abstract:
The 3D capillarity-driven grain growth process was simulated using a modified Potts Monte Carlo technique, starting from two initial microstructures with the grain size distributions well described by Weibull functions of b=2.96 and b=3.47, respectively. The process obeys the grain growth parabolic law very well, with the time exponent n very close to 0.5. The results show that the quasi-stationary grain size distributions finally turn to the same Weibull distribution with b=2.80±0.03 for two different initial microstructures and the grain face number distributions turn to a lognormal distribution. The two analytical 3D grain size distribution functions coincide with the two kinds of functions derived by Liu Guoquan and his coworkers recently based on the different grain growth rate equations.
The 3D capillarity-driven grain growth process was simulated using a modified Potts Monte Carlo technique, starting from two initial microstructures with the grain size distributions well described by Weibull functions of b=2.96 and b=3.47, respectively. The process obeys the grain growth parabolic law very well, with the time exponent n very close to 0.5. The results show that the quasi-stationary grain size distributions finally turn to the same Weibull distribution with b=2.80±0.03 for two different initial microstructures and the grain face number distributions turn to a lognormal distribution. The two analytical 3D grain size distribution functions coincide with the two kinds of functions derived by Liu Guoquan and his coworkers recently based on the different grain growth rate equations.
2009, 38(1):131-137.
Abstract:
Experimental data of Ag/La2NiO4 base electrical contacts in the condition of DC 18V/30A were obtained by electrical contact experimental instrument. The morphology of anode and cathode surface, arc erosion and weight change were analysis. A transient temperature field model of electrical contacts was established by the following procedure analysis: the close arc→ the contact resistance Joule heat → the open arc. The features and distribution of the transient temperature field were calculated by finite element method according to the experimental data. From the results, not only the feature of arc erosion and direction of mass change were predicted, but also the important information about material melting and vaporization were understood, which are valuable to research the erosion mechanism and lifetime for the Ag/La2NiO4 base electrical contacts material.
Experimental data of Ag/La2NiO4 base electrical contacts in the condition of DC 18V/30A were obtained by electrical contact experimental instrument. The morphology of anode and cathode surface, arc erosion and weight change were analysis. A transient temperature field model of electrical contacts was established by the following procedure analysis: the close arc→ the contact resistance Joule heat → the open arc. The features and distribution of the transient temperature field were calculated by finite element method according to the experimental data. From the results, not only the feature of arc erosion and direction of mass change were predicted, but also the important information about material melting and vaporization were understood, which are valuable to research the erosion mechanism and lifetime for the Ag/La2NiO4 base electrical contacts material.
2009, 38(1):138-142.
Abstract:
The (Co43Fe20Ta5.5B31.5)100-xYx（x=0.5, 1, 1.5, 2, 2.5, 3）amorphous ribbons and rods of 2 mm diameters were prepared by melt spinning and copper mold blow- casting method. The analysis of XRD and DSC test indicated that the rod amorphous of 2 mm diameter was easily prepared owing to the alloy (x=3) which the value of x is 3 with maximum glass forming ability. Because the value of the reduced glass transition temperature (Trg) and γ of (Co43Fe20Ta5.5B31.5)97Y3 alloy were 0.657 and 0.436 respectively, which were maximum in the series chemical composition investigated, the glass forming ability of Co-Fe-Ta-B alloy was assessed by Trg and γ.The results of compression test and hysteresis loops showed that the compressive fracture strength and soft magnetic property of the Co-Fe-Ta-B amorphous alloy decreased dramatically when Y was added. The compressive fracture strength and the fracture strain of (Co43Fe20Ta5.5B31.5)97Y3 amorphous rods of 2 mm diameter were 1852 MPa and 0.18%, respectively. Compared with Co43Fe20Ta5.5B31.5, the coercivity Hc was 327×79.6 A/m in the hysteresis loops of the (Co43Fe20Ta5.5B31.5)97Y3 amorphous alloy, at the same time, the saturation magnetic flux density decreased distinctly.
The (Co43Fe20Ta5.5B31.5)100-xYx（x=0.5, 1, 1.5, 2, 2.5, 3）amorphous ribbons and rods of 2 mm diameters were prepared by melt spinning and copper mold blow- casting method. The analysis of XRD and DSC test indicated that the rod amorphous of 2 mm diameter was easily prepared owing to the alloy (x=3) which the value of x is 3 with maximum glass forming ability. Because the value of the reduced glass transition temperature (Trg) and γ of (Co43Fe20Ta5.5B31.5)97Y3 alloy were 0.657 and 0.436 respectively, which were maximum in the series chemical composition investigated, the glass forming ability of Co-Fe-Ta-B alloy was assessed by Trg and γ.The results of compression test and hysteresis loops showed that the compressive fracture strength and soft magnetic property of the Co-Fe-Ta-B amorphous alloy decreased dramatically when Y was added. The compressive fracture strength and the fracture strain of (Co43Fe20Ta5.5B31.5)97Y3 amorphous rods of 2 mm diameter were 1852 MPa and 0.18%, respectively. Compared with Co43Fe20Ta5.5B31.5, the coercivity Hc was 327×79.6 A/m in the hysteresis loops of the (Co43Fe20Ta5.5B31.5)97Y3 amorphous alloy, at the same time, the saturation magnetic flux density decreased distinctly.
2009, 38(1):143-146.
Abstract:
In order to solve the problem of high sintering temperature and reduce the machining costs, the W/ZrC composites were successfully fabricated by the reactive melt penetration (RMP) of Zr2Cu alloy into the porous W/WC presinters at 1400 ℃ for 2 h. Comparing with the conventional powder metallurgy (PM), this process can reduce the fabrication temperature for about 500 ℃. The W/ZrC composites fabricated by this process have homogeneous microstructure and higher relative density with the maximal flexural strength and elastic modulus of 600 MPa and 360 GPa, respectively, and the maximal fracture toughness of 11 MPa·m1/2, four times higher than that of pure ZrC.
In order to solve the problem of high sintering temperature and reduce the machining costs, the W/ZrC composites were successfully fabricated by the reactive melt penetration (RMP) of Zr2Cu alloy into the porous W/WC presinters at 1400 ℃ for 2 h. Comparing with the conventional powder metallurgy (PM), this process can reduce the fabrication temperature for about 500 ℃. The W/ZrC composites fabricated by this process have homogeneous microstructure and higher relative density with the maximal flexural strength and elastic modulus of 600 MPa and 360 GPa, respectively, and the maximal fracture toughness of 11 MPa·m1/2, four times higher than that of pure ZrC.
2009, 38(1):147-150.
Abstract:
Nanoindentation tests have been performed for Cu50Zr43Ti7 bulk metallic glass with a Berkovich indenter and a cube-corner indenter, respectively. It is found that the measured hardness (H) of (6.5±0.2) GPa and the elastic modulus (E) of (114.4±2.1) GPa are independent of the indenter tip shape and the applied indentation loads used in the tests. Many shear bands were observed around the impressions by the cube-corner indenter if compared to with the Berkovich indenter for the alloy without the indentation-size effect (ISE) and strain hardening during the indentation tests. The yield strength (s) of the alloy is about 1.8 GPa by finite element (FE) calculation, good agreement with the experimental results.
Nanoindentation tests have been performed for Cu50Zr43Ti7 bulk metallic glass with a Berkovich indenter and a cube-corner indenter, respectively. It is found that the measured hardness (H) of (6.5±0.2) GPa and the elastic modulus (E) of (114.4±2.1) GPa are independent of the indenter tip shape and the applied indentation loads used in the tests. Many shear bands were observed around the impressions by the cube-corner indenter if compared to with the Berkovich indenter for the alloy without the indentation-size effect (ISE) and strain hardening during the indentation tests. The yield strength (s) of the alloy is about 1.8 GPa by finite element (FE) calculation, good agreement with the experimental results.
2009, 38(1):151-156.
Abstract:
Nanocrystalline nickel and Ni-Fe alloy coatings were synthesized by brush plating using soluble anode. The corrosion characteristics of nanocrystalline nickel, Ni-5.84%Fe and Ni-13.49%Fe alloys were investigated by soak a method and an electrochemical polarization method, respectively. The experimental results indicate that the typical nanocrystalline nickel and Ni-Fe alloy coatings can be synthesized by brush plating, and the alloying element Fe has the effects of solution strengthening and grain size refinement. The nanocrystalline Ni-13.49%Fe alloy is dense in nature and pore free, and exhibits better corrosion resistance in a 3.5 wt% NaCl solution than the nanocrystalline nickel. In 10 wt% HCl solution, the nanocrystalline Ni-13.49%Fe alloy also shows a good corrosion resistance as the nanocrystalline nickel. The surface morphology of all samples after corrosion show a spot corrosion feature in 3.5 wt% NaCl solution, however, the samples are uniformly corroded in 10 wt% HCl solution.
Nanocrystalline nickel and Ni-Fe alloy coatings were synthesized by brush plating using soluble anode. The corrosion characteristics of nanocrystalline nickel, Ni-5.84%Fe and Ni-13.49%Fe alloys were investigated by soak a method and an electrochemical polarization method, respectively. The experimental results indicate that the typical nanocrystalline nickel and Ni-Fe alloy coatings can be synthesized by brush plating, and the alloying element Fe has the effects of solution strengthening and grain size refinement. The nanocrystalline Ni-13.49%Fe alloy is dense in nature and pore free, and exhibits better corrosion resistance in a 3.5 wt% NaCl solution than the nanocrystalline nickel. In 10 wt% HCl solution, the nanocrystalline Ni-13.49%Fe alloy also shows a good corrosion resistance as the nanocrystalline nickel. The surface morphology of all samples after corrosion show a spot corrosion feature in 3.5 wt% NaCl solution, however, the samples are uniformly corroded in 10 wt% HCl solution.
2009, 38(1):157-160.
Abstract:
The 93W-4.5Ni-2.1Fe-0.35Co liquid-phase sintered tungsten heavy alloy (WHA) was fabricated by hot-hydrostatic extrusion at 950 ℃ with plastic deformation ratio of 75%. The specimens for dynamic compression tests were taken from the as-extruded WHA rod along three different directions with the extruding direction. The test results show that the adiabatic shear characteristics of WHA are highly anisotropy for different fiber orientations due to the different adiabatic temperature rise in the different micro-strained condition and the distribution of matrix and fiber.
The 93W-4.5Ni-2.1Fe-0.35Co liquid-phase sintered tungsten heavy alloy (WHA) was fabricated by hot-hydrostatic extrusion at 950 ℃ with plastic deformation ratio of 75%. The specimens for dynamic compression tests were taken from the as-extruded WHA rod along three different directions with the extruding direction. The test results show that the adiabatic shear characteristics of WHA are highly anisotropy for different fiber orientations due to the different adiabatic temperature rise in the different micro-strained condition and the distribution of matrix and fiber.
2009, 38(1):161-163.
Abstract:
SmCo7-xFex(x=0, 0.4, 1, 2) amorphous powders prepared by high-energy milling were sintered into bulk nanocrystalline magnets using spark plasma sintering technique (SPS). XRD patterns show that the powder becomes amorphous after milled for 5 h; and the magnet exhibits stable TbCu7 structure after sintered by SPS. TEM observation indicates that the microstructure of the magnet is composed of SmCo7-xFex single phase grains with an average grain size of 20~50 nm. Magnetic measurement shows that the SmCo6.6Fe0.4 magnet has the magnetic properties as following: iHc=992.8 kA/m，Br=0.634 T, and (BH)max=69.75 kJ/m3.
SmCo7-xFex(x=0, 0.4, 1, 2) amorphous powders prepared by high-energy milling were sintered into bulk nanocrystalline magnets using spark plasma sintering technique (SPS). XRD patterns show that the powder becomes amorphous after milled for 5 h; and the magnet exhibits stable TbCu7 structure after sintered by SPS. TEM observation indicates that the microstructure of the magnet is composed of SmCo7-xFex single phase grains with an average grain size of 20~50 nm. Magnetic measurement shows that the SmCo6.6Fe0.4 magnet has the magnetic properties as following: iHc=992.8 kA/m，Br=0.634 T, and (BH)max=69.75 kJ/m3.
2009, 38(1):164-167.
Abstract:
In order to further enhance shape memory effect (SME) and improve treatment process in Fe-based shape memory alloys, a pre-deformed Fe-Mn-Si-Cr-Ni-Nb-C alloy was subjected to a electropulsing treatment. The results show that the shape memory ratio reached the maximum 80% for the specimen subjected to a 5% pre-deformation and the electropulsing treatment at 300 V and 1 Hz for 13 times, which is 12% greater than that subjected to an ageing at 800 ℃ for 1000 s. In addition, it is found by SEM observation that the electropulsing treatment can induce a large amount of NbC precipitates with small sizes in the bulk at a short time, therefore, improve the shape memory property and increase the efficiency of shape memory effect efficiently.
In order to further enhance shape memory effect (SME) and improve treatment process in Fe-based shape memory alloys, a pre-deformed Fe-Mn-Si-Cr-Ni-Nb-C alloy was subjected to a electropulsing treatment. The results show that the shape memory ratio reached the maximum 80% for the specimen subjected to a 5% pre-deformation and the electropulsing treatment at 300 V and 1 Hz for 13 times, which is 12% greater than that subjected to an ageing at 800 ℃ for 1000 s. In addition, it is found by SEM observation that the electropulsing treatment can induce a large amount of NbC precipitates with small sizes in the bulk at a short time, therefore, improve the shape memory property and increase the efficiency of shape memory effect efficiently.
2009, 38(1):168-171.
Abstract:
La0.7Sr0.3MnO3 (LSMO) target has been prepared by sol-gel method and the thin films of LSMO have been deposited on LaAlO3, SrTiO3, MgO substrates using the pulsed laser deposition technique. The transport and photoinduced properties of LSMO thin films on different substrates have been investigated. It is found that the phase transition temperature decreases and the electrical resistivity increases with decreasing the lattice distortion degrees for the films. The photoinduced properties show that laser induces the increase of electrical resistivity in metallic phase, and the decreases of electrical resistivity in insulating phase. The photoinduced resistivities (Δρ) of films on the MgO and SrTiO3 substrates have a maximum and a minimum due to the competition of double exchange effect and polaron effect.
La0.7Sr0.3MnO3 (LSMO) target has been prepared by sol-gel method and the thin films of LSMO have been deposited on LaAlO3, SrTiO3, MgO substrates using the pulsed laser deposition technique. The transport and photoinduced properties of LSMO thin films on different substrates have been investigated. It is found that the phase transition temperature decreases and the electrical resistivity increases with decreasing the lattice distortion degrees for the films. The photoinduced properties show that laser induces the increase of electrical resistivity in metallic phase, and the decreases of electrical resistivity in insulating phase. The photoinduced resistivities (Δρ) of films on the MgO and SrTiO3 substrates have a maximum and a minimum due to the competition of double exchange effect and polaron effect.
2009, 38(1):172-175.
Abstract:
Li-B Alloy is one kind of thermal battery anode materials with excellent performance but hard to use due to their preparation limits. A scale of 300 g per furnace was achieved by improving the temperature control, cooling system, stirring blade and so on. The alloy prepared by this method was uniform and compact with a density of 0.870 g/cm3, and a tensile strength of 12.61 MPa. The synthesis mechanism and kinetics process were analyzed according to the physical phenomenon as well as XRD results.
Li-B Alloy is one kind of thermal battery anode materials with excellent performance but hard to use due to their preparation limits. A scale of 300 g per furnace was achieved by improving the temperature control, cooling system, stirring blade and so on. The alloy prepared by this method was uniform and compact with a density of 0.870 g/cm3, and a tensile strength of 12.61 MPa. The synthesis mechanism and kinetics process were analyzed according to the physical phenomenon as well as XRD results.
2009, 38(1):176-179.
Abstract:
Thermal barrier coatings (TBCs) comprised of 92 wt.% ZrO2 and 8 wt.% Y2O3 (YSZ); CoNiCrAlY bond coat were deposited by an Air Plasma Spraying (APS) technique. The thermal shock resistance of the TBCs was tested under high temperature wind tunnel. The influence of the high temperature oxidation treatment on the thermal shock resistance of the TBCs was also studied. The results showed that, the TBCs deposited by APS had a good property of thermal shock resistance after 100 cycles. The coating was unabridged and combined well with the substrate, with no spallation of large areas occurring. While the specimens after high temperature oxidation treatment showed poor thermal shock resistance.
Thermal barrier coatings (TBCs) comprised of 92 wt.% ZrO2 and 8 wt.% Y2O3 (YSZ); CoNiCrAlY bond coat were deposited by an Air Plasma Spraying (APS) technique. The thermal shock resistance of the TBCs was tested under high temperature wind tunnel. The influence of the high temperature oxidation treatment on the thermal shock resistance of the TBCs was also studied. The results showed that, the TBCs deposited by APS had a good property of thermal shock resistance after 100 cycles. The coating was unabridged and combined well with the substrate, with no spallation of large areas occurring. While the specimens after high temperature oxidation treatment showed poor thermal shock resistance.
2009, 38(1):180-184.
Abstract:
So far there are a lot of works domestic and abroad about how the pulsed current affects the melts and solidification of alloys, although the results appear uncertain and not systematic due to their different experimental ways, process parameters and conditions. Hereby this paper reviews the world-wide application of the pulsed current on liquid metals, summarizes the effects of pulsed current on the alloys melts and the course of solidification, and analyses their mechanisms. According to our own experimental results, we dig out the existing problems, and point out that the pulsed current is an important external field controlling method with a great potential for manufacturing and casting light-weight and temperature resistant materials used in air and aerospace field.
So far there are a lot of works domestic and abroad about how the pulsed current affects the melts and solidification of alloys, although the results appear uncertain and not systematic due to their different experimental ways, process parameters and conditions. Hereby this paper reviews the world-wide application of the pulsed current on liquid metals, summarizes the effects of pulsed current on the alloys melts and the course of solidification, and analyses their mechanisms. According to our own experimental results, we dig out the existing problems, and point out that the pulsed current is an important external field controlling method with a great potential for manufacturing and casting light-weight and temperature resistant materials used in air and aerospace field.
2009, 38(1):185-188.
Abstract:
TiO2; visible light; modified; tendency
TiO2; visible light; modified; tendency
