Volume 38,Issue 5,2009 Table of Contents
2009, 38(5):753-756.
Abstract:
Zr-Si-N films were prepared by radio frequency powered reactive magnetron sputtering at different N2 partial pressures. The influences of N2 partial pressure on the microstructure and properties of Zr-Si-N films were studied. The results reveal that the Zr/Si ratio decreases and the sheet resistance increases as the N2 partial pressure increases. The microstructures of Zr-Si-N films are composed of nano-crystallite ZrN embedded into amorphous matrix of SiNx phase and a small quantity of Zr2Si produced at low N2 partial pressure. The appearance of Zr2Si phase is related to the low nitridation level. The microhardness of Zr-Si-N film decreases with the increase of N2 partial pressure at the N2 partial pressure of 0.03 Pa, the microhardness of Zr-Si-N films is possessed of maximum value of about 22.5 GPa. The phenomenon that high N2 partial pressure results in low microhardness in Zr-Si-N films may be related to the lattice distortion induced by the addition of Si.
Zr-Si-N films were prepared by radio frequency powered reactive magnetron sputtering at different N2 partial pressures. The influences of N2 partial pressure on the microstructure and properties of Zr-Si-N films were studied. The results reveal that the Zr/Si ratio decreases and the sheet resistance increases as the N2 partial pressure increases. The microstructures of Zr-Si-N films are composed of nano-crystallite ZrN embedded into amorphous matrix of SiNx phase and a small quantity of Zr2Si produced at low N2 partial pressure. The appearance of Zr2Si phase is related to the low nitridation level. The microhardness of Zr-Si-N film decreases with the increase of N2 partial pressure at the N2 partial pressure of 0.03 Pa, the microhardness of Zr-Si-N films is possessed of maximum value of about 22.5 GPa. The phenomenon that high N2 partial pressure results in low microhardness in Zr-Si-N films may be related to the lattice distortion induced by the addition of Si.
2009, 38(5):757-760.
Abstract:
The Mg-based hydrogen storage alloy Mg2-xAlxNi(x=0.1-0.5) was synthesized by combustion synthesis. XRD indicates that a new phase with the cubic Ti2Ni structure appears in the product, and SEM shows that there are a large number of defects on the alloy surface. The effect of partial substitution of Al for Mg on the electrochemical performances of Mg2Ni was investigated. The results show that Al addition affects its electrode characteristics strongly. The electrochemical capacity and cycle lives of Al-containing alloys increase strongly compared to the Al-free alloy. This is attributed to the structure of a new phase (Mg3AlNi2), and the formation of the protect layer of Al2O3. In addition, the results reveal that mechanical grinding is beneficial to improve activation behavior and the maximum electrode capacity, but can not improve the cyclic stability due to breaking of Al2O3 protect layer.
The Mg-based hydrogen storage alloy Mg2-xAlxNi(x=0.1-0.5) was synthesized by combustion synthesis. XRD indicates that a new phase with the cubic Ti2Ni structure appears in the product, and SEM shows that there are a large number of defects on the alloy surface. The effect of partial substitution of Al for Mg on the electrochemical performances of Mg2Ni was investigated. The results show that Al addition affects its electrode characteristics strongly. The electrochemical capacity and cycle lives of Al-containing alloys increase strongly compared to the Al-free alloy. This is attributed to the structure of a new phase (Mg3AlNi2), and the formation of the protect layer of Al2O3. In addition, the results reveal that mechanical grinding is beneficial to improve activation behavior and the maximum electrode capacity, but can not improve the cyclic stability due to breaking of Al2O3 protect layer.
Xue Guanxia
,
Wang Tongmin
,
Su Yanqing
,
Cai Shaowu
,
Xu Jingjing
,
Li Jun
,
Guo Jingjie
,
Li Tingju
2009, 38(5):761-765.
Abstract:
The electromagnetic, thermal and fluid fields during ISM (Induction Skull Melting)of TiAl alloy are simulated. The effects of ampere-turn, frequency and relative position between crucible and coil on the distribution of thermal and flow fields are numerically studied. The simulation model is verified by experiments and the simulation results are discussed in detail
The electromagnetic, thermal and fluid fields during ISM (Induction Skull Melting)of TiAl alloy are simulated. The effects of ampere-turn, frequency and relative position between crucible and coil on the distribution of thermal and flow fields are numerically studied. The simulation model is verified by experiments and the simulation results are discussed in detail
2009, 38(5):766-769.
Abstract:
The effect of various catalysts, such as Ti, Ni, Fe, Ce(SO4)2 and LaCl3, on the reversibility of LiAlH4 was studied by Pressure-Content-Temperature (PCT) experiments. The result indicates that doping induces a marked decrease in the rate of hydrogen release. In addition, doping additives obviously decreases the initial temperature of LiAlH4 of hydrogen release except for doping with LaCl3. However, at the same time, the amount of hydrogen release also decreases. In the study on the hydrogen absorption of LiAlH4 doped with 1mol% Ni, 1mol% Ti, 1 mol% Ce(SO4)2 and 1mol%LaCl3 at 180 ℃ under about 8 MPa, it has been found that the sample doped with 1 mol% Ni presents the largest hydrogen absorption amount with about 0.97wt%.
The effect of various catalysts, such as Ti, Ni, Fe, Ce(SO4)2 and LaCl3, on the reversibility of LiAlH4 was studied by Pressure-Content-Temperature (PCT) experiments. The result indicates that doping induces a marked decrease in the rate of hydrogen release. In addition, doping additives obviously decreases the initial temperature of LiAlH4 of hydrogen release except for doping with LaCl3. However, at the same time, the amount of hydrogen release also decreases. In the study on the hydrogen absorption of LiAlH4 doped with 1mol% Ni, 1mol% Ti, 1 mol% Ce(SO4)2 and 1mol%LaCl3 at 180 ℃ under about 8 MPa, it has been found that the sample doped with 1 mol% Ni presents the largest hydrogen absorption amount with about 0.97wt%.
2009, 38(5):770-773.
Abstract:
The densities of four kinds of molten Ni-based commercial alloys were measured with a modified sessile drop method, and calculated using the calculating software. It is found that the densities of the molten Ni-based commercial alloys decrease and their molar volume increase with increasing of temperature. Compared with the ideal mixing, the molar volumes of the molten Ni-based commercial alloys show negative deviations. It can be attributed to an accommodation between various atoms in the alloys
The densities of four kinds of molten Ni-based commercial alloys were measured with a modified sessile drop method, and calculated using the calculating software. It is found that the densities of the molten Ni-based commercial alloys decrease and their molar volume increase with increasing of temperature. Compared with the ideal mixing, the molar volumes of the molten Ni-based commercial alloys show negative deviations. It can be attributed to an accommodation between various atoms in the alloys
2009, 38(5):774-778.
Abstract:
The residual stress of Ti-6Al-4V alloys by laser solid forming was measured adopting the standard strain gauge technique involving hole drilling method. Sample treatments were divided into three conditions, that is as deposited, annealing and solution aging treatment. The results indicate that the residual stress exhibits the similar distribution along the laser scanning direction (σY) and normal to the scanning direction (σZ). At the location of laser starting scanning, the stress is lower. The largest stress is the compressive stress at the center position and transformed to the highest tensile stress at the location of ending of laser scanning. It can also be found that the residual stress exhibits bigger compressive stress near the substrate, and with increasing of the cladding layer, it develops to lower tensile stress at the top of sample. After annealing treatment, the stress decreases averagely σY for 59.8% and σZ for 72.3%, respectively. After treating by solution aging, the stress decreases averagely σY for 64.7% and σZ for 67.8%, respectively. Heat treatment was found to relieve and adjust the residual stresses of laser solid forming Ti-6Al-4V alloy effectively
The residual stress of Ti-6Al-4V alloys by laser solid forming was measured adopting the standard strain gauge technique involving hole drilling method. Sample treatments were divided into three conditions, that is as deposited, annealing and solution aging treatment. The results indicate that the residual stress exhibits the similar distribution along the laser scanning direction (σY) and normal to the scanning direction (σZ). At the location of laser starting scanning, the stress is lower. The largest stress is the compressive stress at the center position and transformed to the highest tensile stress at the location of ending of laser scanning. It can also be found that the residual stress exhibits bigger compressive stress near the substrate, and with increasing of the cladding layer, it develops to lower tensile stress at the top of sample. After annealing treatment, the stress decreases averagely σY for 59.8% and σZ for 72.3%, respectively. After treating by solution aging, the stress decreases averagely σY for 64.7% and σZ for 67.8%, respectively. Heat treatment was found to relieve and adjust the residual stresses of laser solid forming Ti-6Al-4V alloy effectively
2009, 38(5):779-783.
Abstract:
Based on previous research of Ti40 alloy two typical heat treatments were designed, e.g. 1#, 600 ℃, 4 h AC；2#, 850 ℃, 1 h WQ +550 ℃, 6 h AC. The microstructures , mechanical properties at room-temperature, thermal stability and creep properties of the alloy treated by the two heat treatments were tested. The result show that the difference of their microstructures is mainly in the respect of their grain boundary, e.g. the grain boundary of the alloy by 1# heat treatment is unsmooth and ragged and the ones by 2# heat treatment are smooth and straight. The mechanical properties indicated the difference of the microstructures leads a little effect on properties at room-temperature. Relatively speaking, the microstructure with the unsmooth grain boundary after 1# heat treatment brings good thermal stability and creep properties at lower temperature, and the microstructure with the straight boundary after 2# heat treatment brings good creep properties at higher temperature. The mechanism of the effect of different grain boundaries on thermal stability and creep properties was also discussed in this paper
Based on previous research of Ti40 alloy two typical heat treatments were designed, e.g. 1#, 600 ℃, 4 h AC；2#, 850 ℃, 1 h WQ +550 ℃, 6 h AC. The microstructures , mechanical properties at room-temperature, thermal stability and creep properties of the alloy treated by the two heat treatments were tested. The result show that the difference of their microstructures is mainly in the respect of their grain boundary, e.g. the grain boundary of the alloy by 1# heat treatment is unsmooth and ragged and the ones by 2# heat treatment are smooth and straight. The mechanical properties indicated the difference of the microstructures leads a little effect on properties at room-temperature. Relatively speaking, the microstructure with the unsmooth grain boundary after 1# heat treatment brings good thermal stability and creep properties at lower temperature, and the microstructure with the straight boundary after 2# heat treatment brings good creep properties at higher temperature. The mechanism of the effect of different grain boundaries on thermal stability and creep properties was also discussed in this paper
2009, 38(5):784-787.
Abstract:
The effects of heat treatment on transformation behavior, properties and thermo-mechanical cycling fatigue of Ti49.8Ni50.2 alloy wire were investigated. With increasing of annealing temperature, R→B19′ transformation temperatures increase, while B2→R transformation temperatures decrease. The two transformations temperatures will overlap upon annealing at 823 K. Recovery occurs in the specimen annealed below 823 K, σM decreases slightly with the increase of annealing temperature, The specimen annealed at 723 K shows the largest stable recovery strain while its upon annealing above 823 K, the recrystallization of the specimen will occur, its σM and stable recovery strain decrease sharply, while its fatigue life increases from 103 to 104 magnitudes
The effects of heat treatment on transformation behavior, properties and thermo-mechanical cycling fatigue of Ti49.8Ni50.2 alloy wire were investigated. With increasing of annealing temperature, R→B19′ transformation temperatures increase, while B2→R transformation temperatures decrease. The two transformations temperatures will overlap upon annealing at 823 K. Recovery occurs in the specimen annealed below 823 K, σM decreases slightly with the increase of annealing temperature, The specimen annealed at 723 K shows the largest stable recovery strain while its upon annealing above 823 K, the recrystallization of the specimen will occur, its σM and stable recovery strain decrease sharply, while its fatigue life increases from 103 to 104 magnitudes
2009, 38(5):788-793.
Abstract:
During vacuum arc deposition processes, non-uniformity of thickness and surface properties of deposited films may be induced due to the line-of-sight of vacuum arc plasma. In this paper TiN films were deposited on AISI201 stainless steel horizontally located in front of the arc source and the uniformity of macroparticle, film thickness and surface properties is focused on. The phase structure, surface morphology and corrosion-resistance were analysized by XRD, SEM and electrochemical method. The frictional behavior of uncoated and coated stainless steel was evaluated by pin-on-disk tribometer. The scratch test and micro indentor were utilized to determine the adhesion and hardness of TiN films. The experimental results have demonstrated that TiN film deposited at center site possesses maximal hardness，highest corrosion-resistance and largest thickness. In contrast the TiN films at angle of 20o display minimal thickness and hardness. There are more macroparticles on films deposited at positive angles leading to weak corrosion-resistance. This may be attributed to the force of gas flow induced by pumping system. The friction coefficient and adhesion of TiN films at central site are larger compared to those at other sites.
During vacuum arc deposition processes, non-uniformity of thickness and surface properties of deposited films may be induced due to the line-of-sight of vacuum arc plasma. In this paper TiN films were deposited on AISI201 stainless steel horizontally located in front of the arc source and the uniformity of macroparticle, film thickness and surface properties is focused on. The phase structure, surface morphology and corrosion-resistance were analysized by XRD, SEM and electrochemical method. The frictional behavior of uncoated and coated stainless steel was evaluated by pin-on-disk tribometer. The scratch test and micro indentor were utilized to determine the adhesion and hardness of TiN films. The experimental results have demonstrated that TiN film deposited at center site possesses maximal hardness，highest corrosion-resistance and largest thickness. In contrast the TiN films at angle of 20o display minimal thickness and hardness. There are more macroparticles on films deposited at positive angles leading to weak corrosion-resistance. This may be attributed to the force of gas flow induced by pumping system. The friction coefficient and adhesion of TiN films at central site are larger compared to those at other sites.
2009, 38(5):794-798.
Abstract:
Micro-arc oxidation (MAO) films on pure titanium were prepared in sodium tungsten electrolyte and in potassium dihydrogen phosphate electrolyte, respectively. The surface and cross-section morphologies, the element distribution and the phase composition of coatings were analyzed by means of SEM, EDX, XRD. The photocatalytic activity of the two coatings was tested by UV-Vis spectra. The results show that MAO coatings prepared in the two electrolytes are rough and micro-porous, but the pores on the surface of the coating prepared in the sodium tungsten electrolyte are smaller and more homogeneous. The composition and the phase constitution of the coatings depent on the electrolyte composition, The coating prepared in the sodium tungstate solution mainly consists of elements W, Ti, O, element W is distributed homogeneously in the coating, and the ratio of anatase to rutile is 27:73, while the elements of the coating prepared in the potassium dihydrogen phosphate electrolyte are P, Ti, O, the content of P gradually increased from the surface to the dense layer, and the ratio of anatase to rutile is 84:16. The result of absorbance test shows that the photocatalytic activity of the coating formed in sodium tungsten electrolyte is higher than that of the coating formed in the potassium dihydrogen phosphate electrolyte, because of its larger specific surface area
Micro-arc oxidation (MAO) films on pure titanium were prepared in sodium tungsten electrolyte and in potassium dihydrogen phosphate electrolyte, respectively. The surface and cross-section morphologies, the element distribution and the phase composition of coatings were analyzed by means of SEM, EDX, XRD. The photocatalytic activity of the two coatings was tested by UV-Vis spectra. The results show that MAO coatings prepared in the two electrolytes are rough and micro-porous, but the pores on the surface of the coating prepared in the sodium tungsten electrolyte are smaller and more homogeneous. The composition and the phase constitution of the coatings depent on the electrolyte composition, The coating prepared in the sodium tungstate solution mainly consists of elements W, Ti, O, element W is distributed homogeneously in the coating, and the ratio of anatase to rutile is 27:73, while the elements of the coating prepared in the potassium dihydrogen phosphate electrolyte are P, Ti, O, the content of P gradually increased from the surface to the dense layer, and the ratio of anatase to rutile is 84:16. The result of absorbance test shows that the photocatalytic activity of the coating formed in sodium tungsten electrolyte is higher than that of the coating formed in the potassium dihydrogen phosphate electrolyte, because of its larger specific surface area
2009, 38(5):799-802.
Abstract:
The effects of cold rolling deformation on the damping behavior of Ti50Ni50 alloy were investigated systematically, and the micro-mechanism was discussed. The experiment results show that the damping capacity of deformed Martensite first decreases sharply and then keep constant with the increase of frequency at the low strain amplitude; while it is almost not affected by frequency when strain amplitude is at high level. The damping capacity of deformed martensite decreases with the increase of strain amplitude, and then almost keeps unchanged. When frequency is constant. The high damping property of deformed martensite is attributed to the movements of twin interfaces and dislocations
The effects of cold rolling deformation on the damping behavior of Ti50Ni50 alloy were investigated systematically, and the micro-mechanism was discussed. The experiment results show that the damping capacity of deformed Martensite first decreases sharply and then keep constant with the increase of frequency at the low strain amplitude; while it is almost not affected by frequency when strain amplitude is at high level. The damping capacity of deformed martensite decreases with the increase of strain amplitude, and then almost keeps unchanged. When frequency is constant. The high damping property of deformed martensite is attributed to the movements of twin interfaces and dislocations
2009, 38(5):803-806.
Abstract:
The filling and solidification process of titanium alloy melt in graphite mold was investigated in vertical centrifugal field and in gravity field, respectively. The results show that the process in the former is better than that in the later. The flowability and the filling ability of the melt in the centrifugal field are much improved, it is especially favorable for producing the castings with 3 mm thin wall. The mold can not be fully filled by the melt in the gravity field, in such case the filing resistance is larger than filling force. The full filling can be realized in the centrifugal field. By which the minimum wall thickness of a casting can reach 0.3 mm In addition, under the common action of Coriolis force and centrifugal force, the defects of titanium alloy casting decreases with increasing of rotational velocity
The filling and solidification process of titanium alloy melt in graphite mold was investigated in vertical centrifugal field and in gravity field, respectively. The results show that the process in the former is better than that in the later. The flowability and the filling ability of the melt in the centrifugal field are much improved, it is especially favorable for producing the castings with 3 mm thin wall. The mold can not be fully filled by the melt in the gravity field, in such case the filing resistance is larger than filling force. The full filling can be realized in the centrifugal field. By which the minimum wall thickness of a casting can reach 0.3 mm In addition, under the common action of Coriolis force and centrifugal force, the defects of titanium alloy casting decreases with increasing of rotational velocity
2009, 38(5):807-811.
Abstract:
Carbon fiber reinforced Ti-Al composite was fabricated through infiltration-reaction sythesis process, using Ti powder, Al and carbon fiber as starting materials. The results show that the interface reaction between carbon fiber and Al intensified gradually, the content of TiAl3 increased firstly and then decreased, and Al4C3 and TiC increased with increasing of temperature. Forming of Al2O3 took place in the composite owing to oxygen participating in high temperature stage. The microstructure and phases composition were analyzed by SEM and XRD, and reaction mechanism of the synthesis process among the components of carbon fiber reinforced Ti-Al composite was investigated
Carbon fiber reinforced Ti-Al composite was fabricated through infiltration-reaction sythesis process, using Ti powder, Al and carbon fiber as starting materials. The results show that the interface reaction between carbon fiber and Al intensified gradually, the content of TiAl3 increased firstly and then decreased, and Al4C3 and TiC increased with increasing of temperature. Forming of Al2O3 took place in the composite owing to oxygen participating in high temperature stage. The microstructure and phases composition were analyzed by SEM and XRD, and reaction mechanism of the synthesis process among the components of carbon fiber reinforced Ti-Al composite was investigated
Chen Zili
,
Ma Quan
,
Liu Xianghong
,
Du Shejun
,
Yan Guo
,
Jiao Gaofeng
,
Zhang Pingxiang
,
Zhou Lian
2009, 38(5):812-815.
Abstract:
NbTiTa/Cu superconducting wires were prepared through the thermal diffusion using NbTi sheets and Ta sheets as raw materials. During the process, the rolling and drawing methods were applied after three times extrusion. The superconducting property was measured by the standard method at 4.2 K in High Magnetic Field Laboratory in France. The results indicate that a higher critical current density is obtained in the drawing wires. Jc can reach 791 A/mm2 at 4.2 K and 8 T in the drawing wires with diameter of 1.0 mm. The investigation of microstructure shows that the homogenous filament, homogenous Cu/Sc ratio and same spacing between filaments are found in the drawing wires at the same conditions
NbTiTa/Cu superconducting wires were prepared through the thermal diffusion using NbTi sheets and Ta sheets as raw materials. During the process, the rolling and drawing methods were applied after three times extrusion. The superconducting property was measured by the standard method at 4.2 K in High Magnetic Field Laboratory in France. The results indicate that a higher critical current density is obtained in the drawing wires. Jc can reach 791 A/mm2 at 4.2 K and 8 T in the drawing wires with diameter of 1.0 mm. The investigation of microstructure shows that the homogenous filament, homogenous Cu/Sc ratio and same spacing between filaments are found in the drawing wires at the same conditions
2009, 38(5):812-820.
Abstract:
The structures and hydrogen absorption-desorption properties of V40-Fe8-Ti-Cr(Ti/Cr=0.95~1.20) alloys were investigated. All the studied alloys are single-phase with bcc structure. With the decrease of Ti/Cr ratio, the lattice parameters decrease, plateau pressures increase, and hydrogen absorption capacities increase first, then decrease. The V40Ti26Cr26Fe8 alloy with a Ti/Cr ratio of 1.00 has the maximum hydrogen desorption capacity of 2.4% mass fraction with a plateau pressure of 0.24 MPa at 298 K. ΔH and ΔS of the V40Ti26Cr26Fe8 alloy are –39.6 kJ·mol-1H and –140.3 J·mol-1·K-1, respectively, and its plateau pressure at 423 K is calculated to be 27.5 MPa
The structures and hydrogen absorption-desorption properties of V40-Fe8-Ti-Cr(Ti/Cr=0.95~1.20) alloys were investigated. All the studied alloys are single-phase with bcc structure. With the decrease of Ti/Cr ratio, the lattice parameters decrease, plateau pressures increase, and hydrogen absorption capacities increase first, then decrease. The V40Ti26Cr26Fe8 alloy with a Ti/Cr ratio of 1.00 has the maximum hydrogen desorption capacity of 2.4% mass fraction with a plateau pressure of 0.24 MPa at 298 K. ΔH and ΔS of the V40Ti26Cr26Fe8 alloy are –39.6 kJ·mol-1H and –140.3 J·mol-1·K-1, respectively, and its plateau pressure at 423 K is calculated to be 27.5 MPa
2009, 38(5):821-825.
Abstract:
Acid-proof Ti/SnO2+MnOx/PbO2 anode doped with rare earth Y was prepared by thermal decomposition method and electrodeposited method. The surface characterization of the electrode was characterized by scanning electron microscopy(SEM) and the element composition of layers was analyzed with X-ray Diffraction(XRD). The electrode electrochemical properties were analyzed with Cyclic Voltammogram (CV) and Electrochemical Impedance Spectroscopic (EIS).The influence of Y doping on the service life of the electrode in strong acid solution was emphatically studied. The results indicated that the semiconductive solid solution was formed between Y2O3 and SnO2, which maked the service life of electrode reaching 70 h in high electric density(4 A/cm2); At the same time the oxygen evolution reaction(OER) potential of this electrode reached 2.1 V . The rougher of the surface was, the better its electric catalytic properties were. Ti/SnO2+Y2O3+MnOx/PbO2 electrode is an ideal acid-proof anode material
Acid-proof Ti/SnO2+MnOx/PbO2 anode doped with rare earth Y was prepared by thermal decomposition method and electrodeposited method. The surface characterization of the electrode was characterized by scanning electron microscopy(SEM) and the element composition of layers was analyzed with X-ray Diffraction(XRD). The electrode electrochemical properties were analyzed with Cyclic Voltammogram (CV) and Electrochemical Impedance Spectroscopic (EIS).The influence of Y doping on the service life of the electrode in strong acid solution was emphatically studied. The results indicated that the semiconductive solid solution was formed between Y2O3 and SnO2, which maked the service life of electrode reaching 70 h in high electric density(4 A/cm2); At the same time the oxygen evolution reaction(OER) potential of this electrode reached 2.1 V . The rougher of the surface was, the better its electric catalytic properties were. Ti/SnO2+Y2O3+MnOx/PbO2 electrode is an ideal acid-proof anode material
2009, 38(5):826-829.
Abstract:
By means of finite elements analysis,an investigation has been made for the directional coarsening manners and evolutional rule of γ′ precipitates in a single crystal nickel-base superalloy with [011] orientation during tensile creep at 980 ℃ and 200 MPa. Results show that the von Mises stress in the matrix channel that is 45° with respect to the loading direction is larger than that in the matrix channel that is parallel to the loading direction when external loads applied along the [011] direction. The strain energy change in two kinds of matrix channel is the driving force for the γ′ directional coarsening, the γ′ phase developed along the [010] and [100] and perpendicular to the [001] orientations, and formed lamellar raft morphology inclined 45° angle to the tensile stress axis
By means of finite elements analysis,an investigation has been made for the directional coarsening manners and evolutional rule of γ′ precipitates in a single crystal nickel-base superalloy with [011] orientation during tensile creep at 980 ℃ and 200 MPa. Results show that the von Mises stress in the matrix channel that is 45° with respect to the loading direction is larger than that in the matrix channel that is parallel to the loading direction when external loads applied along the [011] direction. The strain energy change in two kinds of matrix channel is the driving force for the γ′ directional coarsening, the γ′ phase developed along the [010] and [100] and perpendicular to the [001] orientations, and formed lamellar raft morphology inclined 45° angle to the tensile stress axis
2009, 38(5):830-833.
Abstract:
The ablation behaviors of ZrCp/W composites were measured using a plasma ablation equipment. The results indicate that the linear ablation rate increases with increasing of ZrC content and ablation time. The ablation delve and the melted layer with a thickness of 1 mm appeared in the ablated surface. The chemical reaction between the constituted phases was happened in the ablation process, and the new phases were formed. The main ablation mechanism of the composites is the melting ablation which dominated and the thermal chemical ablation which was accompanied
The ablation behaviors of ZrCp/W composites were measured using a plasma ablation equipment. The results indicate that the linear ablation rate increases with increasing of ZrC content and ablation time. The ablation delve and the melted layer with a thickness of 1 mm appeared in the ablated surface. The chemical reaction between the constituted phases was happened in the ablation process, and the new phases were formed. The main ablation mechanism of the composites is the melting ablation which dominated and the thermal chemical ablation which was accompanied
2009, 38(5):834-837.
Abstract:
The stress rupture performances of a directionally solidified Ni-base superalloy DZ951 have been investigated over a wide stress range of 50 to 970 MPa at high temperatures (650 to 1040 ℃). The fracture surface and deformation microstructure were examined by SEM. The results show that the stress rupture strength of DZ951 alloy is much higher than that of DZ40M and almost the same as that of DZ17G alloy. It is suggested that γ′ particles remain cubic shape below 800 ℃, and when the test temperature reaches 900℃, γ′ particles form fine rafted structure. At low temperature (<760 ℃), the fracture mode is cleavage-like. At intermediate temperature (760~850 ℃), the fracture mode shows both cleavage feature and quasi-cleavage feature, and cracks can initiate at the carbide/matrix interface. At high temperature (>850 ℃), the fracture mode turns to be microviod coalessence fracture and the alloy is sensitive to the shrinkage porosity
The stress rupture performances of a directionally solidified Ni-base superalloy DZ951 have been investigated over a wide stress range of 50 to 970 MPa at high temperatures (650 to 1040 ℃). The fracture surface and deformation microstructure were examined by SEM. The results show that the stress rupture strength of DZ951 alloy is much higher than that of DZ40M and almost the same as that of DZ17G alloy. It is suggested that γ′ particles remain cubic shape below 800 ℃, and when the test temperature reaches 900℃, γ′ particles form fine rafted structure. At low temperature (<760 ℃), the fracture mode is cleavage-like. At intermediate temperature (760~850 ℃), the fracture mode shows both cleavage feature and quasi-cleavage feature, and cracks can initiate at the carbide/matrix interface. At high temperature (>850 ℃), the fracture mode turns to be microviod coalessence fracture and the alloy is sensitive to the shrinkage porosity
2009, 38(5):838-841.
Abstract:
CuInS2 (CIS) films were prepared by electrodepositing-sulfurization at the different partial pressures of sulfur r(r=Sn/[N2+Sn]). Their surface morphologies, crystalline structure, electrical and optical properties were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Hall system and ultraviolet-visible (UV-VIS) spectraphotometers, respectively. The results show that the crystalline quality is improved with increasing of r. It is found that the CuInS2 film sulfurized at r=1/2 with the fairly large grain size of about 1 μm has (112) preferred orientation, the carrier concentration is 5.6×1016 cm-3, the optical band gap is about 1.53 eV
CuInS2 (CIS) films were prepared by electrodepositing-sulfurization at the different partial pressures of sulfur r(r=Sn/[N2+Sn]). Their surface morphologies, crystalline structure, electrical and optical properties were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Hall system and ultraviolet-visible (UV-VIS) spectraphotometers, respectively. The results show that the crystalline quality is improved with increasing of r. It is found that the CuInS2 film sulfurized at r=1/2 with the fairly large grain size of about 1 μm has (112) preferred orientation, the carrier concentration is 5.6×1016 cm-3, the optical band gap is about 1.53 eV
2009, 38(5):842-846.
Abstract:
Using Cu, Cr, Nb elemental powders activated by mechanical alloying (MA) for 25 h, the novel-type Cu/Cr2Nb contact materials were fabricated by vacuum hot-pressing at 1000 ℃ for 1 h. The microstructures and the properties of Cu/Cr2Nb contact materials with different compositions were investigated. The results show that Cr2Nb phase can not be synthesized during MA, but can be fully synthesized during vacuum hot-pressing. The prepared Cu/Cr2Nb contact materials have homogeneous and fine microstructures, and Cr2Nb phase sizes fall in several micro. The relative density of Cu/Cr2Nb contact materials with 25%~35% Cr2Nb is comparable with those of CuCr50 prepared by conventional or infiltrating process, but the hardness and conductivity of the former are obviously superior to those of the latter
Using Cu, Cr, Nb elemental powders activated by mechanical alloying (MA) for 25 h, the novel-type Cu/Cr2Nb contact materials were fabricated by vacuum hot-pressing at 1000 ℃ for 1 h. The microstructures and the properties of Cu/Cr2Nb contact materials with different compositions were investigated. The results show that Cr2Nb phase can not be synthesized during MA, but can be fully synthesized during vacuum hot-pressing. The prepared Cu/Cr2Nb contact materials have homogeneous and fine microstructures, and Cr2Nb phase sizes fall in several micro. The relative density of Cu/Cr2Nb contact materials with 25%~35% Cr2Nb is comparable with those of CuCr50 prepared by conventional or infiltrating process, but the hardness and conductivity of the former are obviously superior to those of the latter
2009, 38(5):847-850.
Abstract:
Amorphous Fe78Si9B13 alloys were treated by low frequency pulse magnetic field. The temperature rise in the course of the treatment of pulsed magnetic field was measured by a non-contact infrared thermometer. The microstructure changes of amorphous specimens after treatment were observed by M?ssbauer spectroscopy and TEM. The results show that the nanocrystallization of amorphous specimens can occur at low temperature. When the temperature rise is under 7 ℃, the precipitation content and the grain size of the nanocrystalline phase α-Fe(Si) with bcc crystal structure are about 2.18%~9.43% and 10 nm, Respectively. Compared with the original amorphous alloy, the double- phase (amorphous nanocrystaline) nanocrystalline alloy has obvious high mean hyperfine magnetic field
Amorphous Fe78Si9B13 alloys were treated by low frequency pulse magnetic field. The temperature rise in the course of the treatment of pulsed magnetic field was measured by a non-contact infrared thermometer. The microstructure changes of amorphous specimens after treatment were observed by M?ssbauer spectroscopy and TEM. The results show that the nanocrystallization of amorphous specimens can occur at low temperature. When the temperature rise is under 7 ℃, the precipitation content and the grain size of the nanocrystalline phase α-Fe(Si) with bcc crystal structure are about 2.18%~9.43% and 10 nm, Respectively. Compared with the original amorphous alloy, the double- phase (amorphous nanocrystaline) nanocrystalline alloy has obvious high mean hyperfine magnetic field
2009, 38(5):851-856.
Abstract:
The Co43Fe20Ta5.5B31.5 amorphous ribbons were prepared by melt spinning. The effects of the crystallization under isothermal and non-isothermal conditions on microstructure and magnetic properties were investigated using X-ray diffraction (XRD), differential thermal analyzer (DTA), and vibrating samples magnetometer (VSM). It is found that the saturation magnetization Ms and the coercivity Hc increase with increasing of the crystallized volume fraction α under the condition of isothermal annealing. The Hc value of the alloy changes from 1.25×79.6 A/m for as-cast sample to 634.45×79.6 A/m for sample annealed at 928 K for 55 min, and at the same time the Ms value changes from 37.2 to 58.4 (A·m2)·kg-1. In the initial crystallization stage, the primary crystallization product is (Co, Fe)21Ta2B6 crystal, and the values of Hc and Ms increases gradually with increasing of α. Along with the development of crystallization, the values of Hc and Ms increase sharply when (Co, Fe)B and (Co, Fe)3B2 crystals precipitate. Under the non-isothermal crystallization conditions, the value of Ms increases monotonously with increasing of the stopping temperature, but the increase amplitude is very small. The value of Hc varies substantially with increasing of the stopping temperature, and the varying is non-monotonous. Within the temperature range of the first crystallization peak, the value of Hc increases monotonously with increasing of the stopping temperature. When the stopping temperature is higher then that of ending of the second crystallization peak, the value of Hc decreases drastically. When the stopping temperature increases from 968 to1153 K, the values of Ms and Hc increase from 61.74 to 67.7 A·m2/kg and from 267.6×79.6 to 416.2×79.6A/m, respectively. The Hc value decreases to 152.2×79.6 A/m when stopping temperature is up to 1273 K
The Co43Fe20Ta5.5B31.5 amorphous ribbons were prepared by melt spinning. The effects of the crystallization under isothermal and non-isothermal conditions on microstructure and magnetic properties were investigated using X-ray diffraction (XRD), differential thermal analyzer (DTA), and vibrating samples magnetometer (VSM). It is found that the saturation magnetization Ms and the coercivity Hc increase with increasing of the crystallized volume fraction α under the condition of isothermal annealing. The Hc value of the alloy changes from 1.25×79.6 A/m for as-cast sample to 634.45×79.6 A/m for sample annealed at 928 K for 55 min, and at the same time the Ms value changes from 37.2 to 58.4 (A·m2)·kg-1. In the initial crystallization stage, the primary crystallization product is (Co, Fe)21Ta2B6 crystal, and the values of Hc and Ms increases gradually with increasing of α. Along with the development of crystallization, the values of Hc and Ms increase sharply when (Co, Fe)B and (Co, Fe)3B2 crystals precipitate. Under the non-isothermal crystallization conditions, the value of Ms increases monotonously with increasing of the stopping temperature, but the increase amplitude is very small. The value of Hc varies substantially with increasing of the stopping temperature, and the varying is non-monotonous. Within the temperature range of the first crystallization peak, the value of Hc increases monotonously with increasing of the stopping temperature. When the stopping temperature is higher then that of ending of the second crystallization peak, the value of Hc decreases drastically. When the stopping temperature increases from 968 to1153 K, the values of Ms and Hc increase from 61.74 to 67.7 A·m2/kg and from 267.6×79.6 to 416.2×79.6A/m, respectively. The Hc value decreases to 152.2×79.6 A/m when stopping temperature is up to 1273 K
2009, 38(5):857-861.
Abstract:
The phase structure and electrochemical properties of La0.67Mg0.33Ni2.5Cu0.5 alloys as cast and treated by heat treatment and magnetic-heat treatment were studied in this paper. The influence of the heat treatment and magnetic-heat treatment as well as Ni substituted partly with Cu on the phase structure and electrochemical properties of La-Mg-Ni-Cu alloys were investigated by XRD and SEM analysis. The results show that the retention of discharge capacity of as-cast La0.67Mg0.33Ni2.5Cu0.5 alloy is increased to 72.44% from 64.40% after 50 cycles. The maximum discharge capacity of La0.67Mg0.33Ni2.5Cu0.5 alloy after magnetic-heat treatment is 328.2mAh/g, which is 31.51% larger than that of La0.67Mg0.33Ni2.5Cu0.5 alloy after heat treatment. Its retention of discharge capacity is 75.89% after 50 cycles. The characteristic of discharge voltage platform is much flatter and longer, the limit current density is increased and the diffusion speed of hydrogen in the alloys increases.
The phase structure and electrochemical properties of La0.67Mg0.33Ni2.5Cu0.5 alloys as cast and treated by heat treatment and magnetic-heat treatment were studied in this paper. The influence of the heat treatment and magnetic-heat treatment as well as Ni substituted partly with Cu on the phase structure and electrochemical properties of La-Mg-Ni-Cu alloys were investigated by XRD and SEM analysis. The results show that the retention of discharge capacity of as-cast La0.67Mg0.33Ni2.5Cu0.5 alloy is increased to 72.44% from 64.40% after 50 cycles. The maximum discharge capacity of La0.67Mg0.33Ni2.5Cu0.5 alloy after magnetic-heat treatment is 328.2mAh/g, which is 31.51% larger than that of La0.67Mg0.33Ni2.5Cu0.5 alloy after heat treatment. Its retention of discharge capacity is 75.89% after 50 cycles. The characteristic of discharge voltage platform is much flatter and longer, the limit current density is increased and the diffusion speed of hydrogen in the alloys increases.
2009, 38(5):862-865.
Abstract:
To evaluate the effect of CeO2 on the microstructure and property of SiO2-Al2O3-MgO-Na2O-K2O-F system, 2wt%, 3wt%, 4wt%, 5wt% CeO2 were added respectively. Crystallization behaviors, crystalline phases, microstructures of the glass-ceramics with various compositions were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron micro scope (SEM) analysis. Three-point bending strength, micro hardness, machinability and wear abrationlosing weight were also measured. The results revealed that the main crystalline phase of glass ceramics wasn’t changed, but the aspect ratio of mica crystals increased upon adding CeO2 With increasing of the CeO2 content, the three-point bending strength firstly increased and then decreased, microhardness firstly decreased and then increased, wear resistance decreased and machinability increased obviously. The addition of 3% CeO2 enhanced bending strength of SiO2-Al2O3-MgO-Na2O-K2O-F glass-ceramics at the same time could give appropriate color similar to teeth. The excessive addition would be unbeneficial to improving of bending strength and wear resistance
To evaluate the effect of CeO2 on the microstructure and property of SiO2-Al2O3-MgO-Na2O-K2O-F system, 2wt%, 3wt%, 4wt%, 5wt% CeO2 were added respectively. Crystallization behaviors, crystalline phases, microstructures of the glass-ceramics with various compositions were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron micro scope (SEM) analysis. Three-point bending strength, micro hardness, machinability and wear abrationlosing weight were also measured. The results revealed that the main crystalline phase of glass ceramics wasn’t changed, but the aspect ratio of mica crystals increased upon adding CeO2 With increasing of the CeO2 content, the three-point bending strength firstly increased and then decreased, microhardness firstly decreased and then increased, wear resistance decreased and machinability increased obviously. The addition of 3% CeO2 enhanced bending strength of SiO2-Al2O3-MgO-Na2O-K2O-F glass-ceramics at the same time could give appropriate color similar to teeth. The excessive addition would be unbeneficial to improving of bending strength and wear resistance
2009, 38(5):866-869.
Abstract:
Rare earth elements are recognized as the “vitamin” of metals, and trace amount of rare earth Ce can effectively improve the comprehensive properties of the solder alloy. However, rapid tin whisker growth has been found when excessive amount of rare earth were doped in the solder alloys. The results indicated that the rare earth-phase will be oxidized and induce volume expansion when Sn 3.8Ag0.7Cu1.0Ce solder was exposed in air, and the constraint action of the solder matrix on the volume expansion of the oxidized rare earth-phase will result in a compressive stress that will accelerate the growth of tin whiskers
Rare earth elements are recognized as the “vitamin” of metals, and trace amount of rare earth Ce can effectively improve the comprehensive properties of the solder alloy. However, rapid tin whisker growth has been found when excessive amount of rare earth were doped in the solder alloys. The results indicated that the rare earth-phase will be oxidized and induce volume expansion when Sn 3.8Ag0.7Cu1.0Ce solder was exposed in air, and the constraint action of the solder matrix on the volume expansion of the oxidized rare earth-phase will result in a compressive stress that will accelerate the growth of tin whiskers
