Volume 42,Issue 1,2013 Table of Contents
2013, 42(1):1-5.
Abstract:
In order to improve the hydrogen storage characteristics of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by Mn. Rapid quenching technology was used to prepare the Mg20Ni10-xMnx (x=0, 1, 2, 3, 4) hydrogen storage alloys. The microstructures of the as-cast and quenched alloys were characterized by XRD and HRTEM. The hydriding and dehydriding kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical performances were tested by an automatic galvanostatic system. The results show that, as the quenching rate reaches to 20 m/s, an amorphous phase can be detected in the (x=4) alloy, and the amorphization degree of the alloy visibly increases with the growing of the quenching rate. The rapid quenching improves the hydrogen absorption and desorption characteristics of the alloy dramatically. Additionally, it also enhances the electrochemical hydrogen storage performances greatly, including the discharge capacity and cycle stability of the alloys substituted by Mn
In order to improve the hydrogen storage characteristics of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by Mn. Rapid quenching technology was used to prepare the Mg20Ni10-xMnx (x=0, 1, 2, 3, 4) hydrogen storage alloys. The microstructures of the as-cast and quenched alloys were characterized by XRD and HRTEM. The hydriding and dehydriding kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical performances were tested by an automatic galvanostatic system. The results show that, as the quenching rate reaches to 20 m/s, an amorphous phase can be detected in the (x=4) alloy, and the amorphization degree of the alloy visibly increases with the growing of the quenching rate. The rapid quenching improves the hydrogen absorption and desorption characteristics of the alloy dramatically. Additionally, it also enhances the electrochemical hydrogen storage performances greatly, including the discharge capacity and cycle stability of the alloys substituted by Mn
2013, 42(1):6-13.
Abstract:
This work investigated the refinement of Al3Ni phase in Ni-7050 composite, which was prepared by the melting reaction with two different components, 5% and 10% Ni added in 7050 aluminium alloy. Hardness tests, metallographic observation, SEM and DSC were used to analyze the structures and performances. The results show that the hardness of the two composites was obviously increased to 1918 and 2364 MPa after T6 aging. Fracture analysis shows that the fracture mechanism was mainly Al3Ni brittle fracture and interfaces debond. Experiments were designed to investigate the influences of annealing/rolling treatment on structures and properties of the composites. The results indicated: (1) Long time annealing treatment could induce refinement and spheroidization of the Al3Ni phase. With the annealing time prolonged, the hardness first increased and then decreased. (2) After multi-step hot/cold rolling, the microscopic structure of composites showed that the size of Al3Ni phase changed progressively, Al3Ni phase was smashed and transformed from original long slab to nearly isometric particles
This work investigated the refinement of Al3Ni phase in Ni-7050 composite, which was prepared by the melting reaction with two different components, 5% and 10% Ni added in 7050 aluminium alloy. Hardness tests, metallographic observation, SEM and DSC were used to analyze the structures and performances. The results show that the hardness of the two composites was obviously increased to 1918 and 2364 MPa after T6 aging. Fracture analysis shows that the fracture mechanism was mainly Al3Ni brittle fracture and interfaces debond. Experiments were designed to investigate the influences of annealing/rolling treatment on structures and properties of the composites. The results indicated: (1) Long time annealing treatment could induce refinement and spheroidization of the Al3Ni phase. With the annealing time prolonged, the hardness first increased and then decreased. (2) After multi-step hot/cold rolling, the microscopic structure of composites showed that the size of Al3Ni phase changed progressively, Al3Ni phase was smashed and transformed from original long slab to nearly isometric particles
2013, 42(1):14-18.
Abstract:
Based on the research on the solidification of twin-roll continuous casting aluminum alloy thin strip, the analytical model of heterogeneous nucleation, the growth kinetics of tip (KGT) and columnar dendrite transformation to equiaxed dendrite (CET) of twin-roll continuous casting aluminum alloy thin strip solidification are established by means of the principle of metal solidification. Meantime based on the cellular automaton(CA), the emulational model of twin-roll continuous casting aluminum alloy thin strip solidification is established. The foundation for the emulational simulation of twin-roll continuous casting thin strip solidification structure is laid. Last, the numerical simulation can provide some theoretical guidance for twin-roll continuous casting thin strip. Meanwhile it has confirmed the mathematical simulation feasibility by the solidification process of twin-roll continuous casting aluminum alloy thin strip
Based on the research on the solidification of twin-roll continuous casting aluminum alloy thin strip, the analytical model of heterogeneous nucleation, the growth kinetics of tip (KGT) and columnar dendrite transformation to equiaxed dendrite (CET) of twin-roll continuous casting aluminum alloy thin strip solidification are established by means of the principle of metal solidification. Meantime based on the cellular automaton(CA), the emulational model of twin-roll continuous casting aluminum alloy thin strip solidification is established. The foundation for the emulational simulation of twin-roll continuous casting thin strip solidification structure is laid. Last, the numerical simulation can provide some theoretical guidance for twin-roll continuous casting thin strip. Meanwhile it has confirmed the mathematical simulation feasibility by the solidification process of twin-roll continuous casting aluminum alloy thin strip
2013, 42(1):19-22.
Abstract:
A Vibrating Sample Magnetometer (VSM) and a set-up for electrical impedance measurement in magnetic field were employed to study Co30Ag70 mechanical alloys with additions of 0%, 5% and 10% (mass fraction) hard magnetic SmCo5. With increasing SmCo5 content, the particulate composites exhibited an increase in the remanent magnetization when the coercive field remained rather constant. The electrical impedance of each composite did not show a large variation between 10 kHz and 100 kHz but rapidly rose with the increase in frequency from around 200 kHz to 1 MHz due to the skin effect. All impedance spectra were slightly shifted when the magnetic field of 3.3 kA/m was applied. The largest difference was observed in the case of Co30Ag70 without SmCo5 addition. The results confirmed the relationship between the magnetic softness of materials and their electrical impedance in magnetic field
A Vibrating Sample Magnetometer (VSM) and a set-up for electrical impedance measurement in magnetic field were employed to study Co30Ag70 mechanical alloys with additions of 0%, 5% and 10% (mass fraction) hard magnetic SmCo5. With increasing SmCo5 content, the particulate composites exhibited an increase in the remanent magnetization when the coercive field remained rather constant. The electrical impedance of each composite did not show a large variation between 10 kHz and 100 kHz but rapidly rose with the increase in frequency from around 200 kHz to 1 MHz due to the skin effect. All impedance spectra were slightly shifted when the magnetic field of 3.3 kA/m was applied. The largest difference was observed in the case of Co30Ag70 without SmCo5 addition. The results confirmed the relationship between the magnetic softness of materials and their electrical impedance in magnetic field
2013, 42(1):23-27.
Abstract:
TiAl alloys with a composition of Ti-45Al-2Cr-2Nb-1B-0.5Ta(at%) (TA alloy) and Ti-45Al-2Cr-2Nb-1B-0.5Ta- 0.225Y(at%) (TAY alloy) were prepared by double mechanical milling and spark plasma sintering (SPS). The effect of Y addition on microstructure and mechanical properties of TiAl-based alloys was studied. The results show that the morphology of double mechanical milling powder is regular with sizes in the range of 20~40 μm. The main phases of TiAl and Ti3Al and few phases of Ti2Al and TiB2 were observed in the SPS bulk samples of TiAl-based alloys. The equiaxed crystal grain microstructure was achieved with sizes in the range of 100~400 nm in TA alloy samples. The samples exhibited compressive properties at room temperature with a compressive strength of 2614 MPa and a compression ratio of 20.57%. For TAY alloy, the sizes of equiaxed crystal grain obviously decreased. The samples exhibited compressive properties at room temperature with a compressive strength of 2677 MPa and a compression ratio of 22.91%. The micro-hardness of the SPS bulk samples of TA alloy was obviously higher than that of the SPS bulk samples of TAY alloy. On the base of analysis of fractographs, it showed that the compression fracture transform of the SPS TiAl-based alloys samples was intergranular rupture
TiAl alloys with a composition of Ti-45Al-2Cr-2Nb-1B-0.5Ta(at%) (TA alloy) and Ti-45Al-2Cr-2Nb-1B-0.5Ta- 0.225Y(at%) (TAY alloy) were prepared by double mechanical milling and spark plasma sintering (SPS). The effect of Y addition on microstructure and mechanical properties of TiAl-based alloys was studied. The results show that the morphology of double mechanical milling powder is regular with sizes in the range of 20~40 μm. The main phases of TiAl and Ti3Al and few phases of Ti2Al and TiB2 were observed in the SPS bulk samples of TiAl-based alloys. The equiaxed crystal grain microstructure was achieved with sizes in the range of 100~400 nm in TA alloy samples. The samples exhibited compressive properties at room temperature with a compressive strength of 2614 MPa and a compression ratio of 20.57%. For TAY alloy, the sizes of equiaxed crystal grain obviously decreased. The samples exhibited compressive properties at room temperature with a compressive strength of 2677 MPa and a compression ratio of 22.91%. The micro-hardness of the SPS bulk samples of TA alloy was obviously higher than that of the SPS bulk samples of TAY alloy. On the base of analysis of fractographs, it showed that the compression fracture transform of the SPS TiAl-based alloys samples was intergranular rupture
2013, 42(1):28-31.
Abstract:
Mg-50%Al4C3-6%Ce master alloy has been prepared by powder in-situ synthesis process. Phases compositions, micro-morphology and micro-area composition were analyzed by XRD (X-ray diffraction), SEM (scanning electron microscope) and EDS (energy dispersive spectrometer). The results show that the master alloy mainly contains lamellar Al4C3, rod-shaped Al4Ce and Mg. The microstructure of AZ91D alloy is obviously refined after Mg-50%Al4C3-6%Ce master alloy addition. The dendritic morphology of α-Mg evolves from a characteristic six-fold symmetrical shape to a petal-like shape. After adding 1.2wt% master alloy to AZ91D magnesium alloy, the average grain size is obviously decreased from 360 to 65 μm. The mechanism of grain refinement is ascribed to the Al4C3 particles acting as heterogeneous crystal nucleus of primary α-Mg and Ce can activate the potential Al4C3 particles on the solid-liquid interface
Mg-50%Al4C3-6%Ce master alloy has been prepared by powder in-situ synthesis process. Phases compositions, micro-morphology and micro-area composition were analyzed by XRD (X-ray diffraction), SEM (scanning electron microscope) and EDS (energy dispersive spectrometer). The results show that the master alloy mainly contains lamellar Al4C3, rod-shaped Al4Ce and Mg. The microstructure of AZ91D alloy is obviously refined after Mg-50%Al4C3-6%Ce master alloy addition. The dendritic morphology of α-Mg evolves from a characteristic six-fold symmetrical shape to a petal-like shape. After adding 1.2wt% master alloy to AZ91D magnesium alloy, the average grain size is obviously decreased from 360 to 65 μm. The mechanism of grain refinement is ascribed to the Al4C3 particles acting as heterogeneous crystal nucleus of primary α-Mg and Ce can activate the potential Al4C3 particles on the solid-liquid interface
2013, 42(1):33-36.
Abstract:
Ag-1.33Mg-0.54Ni (at%) alloy with high strength and high electrical conductivity, was subjected to accumulative rolling with 98% thickness reduction and internal oxidation, and studied by scan electron microscope (SEM) and X-ray diffraction (XRD). Conventional mechanical properties before and after internal oxidation were evaluated. Results show that the hardness, tensile strength, tensile elongation and electrical resistivity of the alloy after internal oxidation were 1350 MPa, 450 MPa, 6% and 1.73 μΩ·cm, respectively. Further, texture studies suggest that the alloy during internal oxidation had the {110}<001> Goss and {110}<112> Brass textures. A few of MgO and NiO precipitates in a silver matrix hindered the growth of Ag grains and kept the orientation of Ag grains quite stable and enhanced the mechanical properties of the alloy
Ag-1.33Mg-0.54Ni (at%) alloy with high strength and high electrical conductivity, was subjected to accumulative rolling with 98% thickness reduction and internal oxidation, and studied by scan electron microscope (SEM) and X-ray diffraction (XRD). Conventional mechanical properties before and after internal oxidation were evaluated. Results show that the hardness, tensile strength, tensile elongation and electrical resistivity of the alloy after internal oxidation were 1350 MPa, 450 MPa, 6% and 1.73 μΩ·cm, respectively. Further, texture studies suggest that the alloy during internal oxidation had the {110}<001> Goss and {110}<112> Brass textures. A few of MgO and NiO precipitates in a silver matrix hindered the growth of Ag grains and kept the orientation of Ag grains quite stable and enhanced the mechanical properties of the alloy
2013, 42(1):37-42.
Abstract:
The uniaxial compressive fracture behavior of a Hf44.5Cu27Ni13.5Ti5Al10 bulk metallic glass (BMG) was investigated at different strain rates (10-4~103 s-1) by an INSTRON-5569 testing machine and Split Hopkinson Pressure Bar. The results show that the Hf44.5Cu27Ni13.5Ti5Al10 bulk metallic glass isn’t sensitive to strain rate under the quasi-static compression condition. The fracture strength is 2400 MPa. The fracture strength is 2840 MPa under the dynamic compression. The dimple structure and periodical corrugation formed at the fracture surface were observed. The fracture mechanism attributed to ductile fracture in the range of micro-scale. In addition, interaction of elastic waves and the dynamic crack front plays an important role during the formation of periodic corrugations. The higher fracture stress and adiabatic temperature are caused by the higher dynamic compressive strain rate. Phase separation was formed by segregation and diffusion at the interface during compression and affected the formation of shear cracks/bands.
The uniaxial compressive fracture behavior of a Hf44.5Cu27Ni13.5Ti5Al10 bulk metallic glass (BMG) was investigated at different strain rates (10-4~103 s-1) by an INSTRON-5569 testing machine and Split Hopkinson Pressure Bar. The results show that the Hf44.5Cu27Ni13.5Ti5Al10 bulk metallic glass isn’t sensitive to strain rate under the quasi-static compression condition. The fracture strength is 2400 MPa. The fracture strength is 2840 MPa under the dynamic compression. The dimple structure and periodical corrugation formed at the fracture surface were observed. The fracture mechanism attributed to ductile fracture in the range of micro-scale. In addition, interaction of elastic waves and the dynamic crack front plays an important role during the formation of periodic corrugations. The higher fracture stress and adiabatic temperature are caused by the higher dynamic compressive strain rate. Phase separation was formed by segregation and diffusion at the interface during compression and affected the formation of shear cracks/bands.
2013, 42(1):43-48.
Abstract:
The significant springback occurring after unloading in numerically controlled (NC) bending of high strength (HS) titanium alloy tube will affect the geometric and shape accuracy severely. A 3D elastic-plastic FEM containing NC bending, mandrel retracting and springback process of HS TA18 tube was established based on ABAQUS platform, and reliability assessment has been carried out. The influence significance and rules of processing parameters on springback of HS TA18 tube have been investigated by means of virtual orthogonal tests. It is shown that mandrel protrusion length, friction coefficient between bending die and tube, clearance between pressure die and tube, relative boosting velocity and clearance between mandrel and tube have a significant influence on springback. The mandrel protrusion length has the negative effect on the springback angle. The friction coefficient between bending die and tube, clearance between pressure die and tube, as well as clearance between mandrel and tube have the positive effects. The springback angle increases obviously when relative boosting velocity is lower than 1. Moreover, the prediction model between springback angle and significant processing parameters was established by multi-linear stepwise regression. Compared with virtual tests results, the relative error is less than 5% for φ12 mm×t1 mm×R36 mm HS TA18 tube
The significant springback occurring after unloading in numerically controlled (NC) bending of high strength (HS) titanium alloy tube will affect the geometric and shape accuracy severely. A 3D elastic-plastic FEM containing NC bending, mandrel retracting and springback process of HS TA18 tube was established based on ABAQUS platform, and reliability assessment has been carried out. The influence significance and rules of processing parameters on springback of HS TA18 tube have been investigated by means of virtual orthogonal tests. It is shown that mandrel protrusion length, friction coefficient between bending die and tube, clearance between pressure die and tube, relative boosting velocity and clearance between mandrel and tube have a significant influence on springback. The mandrel protrusion length has the negative effect on the springback angle. The friction coefficient between bending die and tube, clearance between pressure die and tube, as well as clearance between mandrel and tube have the positive effects. The springback angle increases obviously when relative boosting velocity is lower than 1. Moreover, the prediction model between springback angle and significant processing parameters was established by multi-linear stepwise regression. Compared with virtual tests results, the relative error is less than 5% for φ12 mm×t1 mm×R36 mm HS TA18 tube
2013, 42(1):49-53.
Abstract:
The effects of different oxidation treatment temperatures on the oxidation layer color for TC21 titanium alloy were investigated, and the microstructure and mechanical property of the alloy after oxidation treatment were analyzed. The results show that after oxidation treatment, the color of oxidation layer presents particular change. The colors of oxidation layer become deeper with the increase temperature, and the mechanical property of TC21 titanium alloy is decreased. The oxidation color and the mechanical property of TC21 titanium have certain corresponding relations. When the oxidation treatment is 600 °C，the alloy shows dark blue, and the mechanical property could meet the requirements for utilization; when temperature of oxidation higher than 600 °C, the color of oxidation layer turns to darken, and the mechanical property could not meet the requirements for utilization
The effects of different oxidation treatment temperatures on the oxidation layer color for TC21 titanium alloy were investigated, and the microstructure and mechanical property of the alloy after oxidation treatment were analyzed. The results show that after oxidation treatment, the color of oxidation layer presents particular change. The colors of oxidation layer become deeper with the increase temperature, and the mechanical property of TC21 titanium alloy is decreased. The oxidation color and the mechanical property of TC21 titanium have certain corresponding relations. When the oxidation treatment is 600 °C，the alloy shows dark blue, and the mechanical property could meet the requirements for utilization; when temperature of oxidation higher than 600 °C, the color of oxidation layer turns to darken, and the mechanical property could not meet the requirements for utilization
2013, 42(1):54-57.
Abstract:
Experiments of electron beam welding was carried out for a 50 mm thick TC4-DT titanium alloy. The effect of electron beam welding on the microstructure characteristics was investigated using optical microscope observation and microhardness measurement for the cross-section of the welded joints. The results show that the microstructure of base metal was typical bimodal structure composed of primary α phase and lamellar (α+β). The microstructure of weld metal was basket-like martensite α′. Coursed primary β grain boundaries were clear in upper and middle parts of weld metal, while the size of the β grains was small and the grain boundaries were not obvious in the bottom. The microstructure of heat affected zone (HAZ) may be divided into two regions. The microstructure of HAZ near fusion zone was consisted of little primary α phase and needle martensite α′, while the microstructure near base metal was constituted of primary α phase and transferred β containing aciculate α. The boundary of the two regions was dependent on the β phase transfer temperature during weld cooling. The microhardness of the weld metal and HAZ was higher than that of base metal, and there was a peak value of microhardness in the HAZ near fusion zone. In addition, the microhardness of the fusion zone had an increased tendency with the measured weld depth increasing
Experiments of electron beam welding was carried out for a 50 mm thick TC4-DT titanium alloy. The effect of electron beam welding on the microstructure characteristics was investigated using optical microscope observation and microhardness measurement for the cross-section of the welded joints. The results show that the microstructure of base metal was typical bimodal structure composed of primary α phase and lamellar (α+β). The microstructure of weld metal was basket-like martensite α′. Coursed primary β grain boundaries were clear in upper and middle parts of weld metal, while the size of the β grains was small and the grain boundaries were not obvious in the bottom. The microstructure of heat affected zone (HAZ) may be divided into two regions. The microstructure of HAZ near fusion zone was consisted of little primary α phase and needle martensite α′, while the microstructure near base metal was constituted of primary α phase and transferred β containing aciculate α. The boundary of the two regions was dependent on the β phase transfer temperature during weld cooling. The microhardness of the weld metal and HAZ was higher than that of base metal, and there was a peak value of microhardness in the HAZ near fusion zone. In addition, the microhardness of the fusion zone had an increased tendency with the measured weld depth increasing
2013, 42(1):58-63.
Abstract:
The deformation mechanism of titanium alloy at every stage during hot deformation was discussed, based on the characteristics of flow stress curves with discontinuous yielding. A viscoplastic constitutive model was built on the premise that the discontinuous yielding phenomenon was associated with the rapid dislocation multiplication at an early stage of yielding and the unified viscoplastic theory. In this model, the effect of deformation temperature and strain rate was considered. This model can describe the discontinuous yielding phenomenon, the slight degree of strain hardening after the low yield point and the mechanism of dynamic recrystallization when the strain achieved to the critical value where the dynamic recrystallization takes place. Applying the constitutive model to the isothermal compression of one new kind of metastable beta Ti2448 titanium alloy, the material constants in the model were identified by the GA-based global optimization method which was adopted in this paper. The relative difference between the predicted and experimental values is less than 5%, which implies that this constitutive model with high prediction based on the internal state variables can not only offer clear physical insight, but also can describe the flow behaviors of Ti2448 titanium alloy during hot deformation with discontinuous yielding. The generality of this model makes it possible to extend the theory to other titanium alloys that have discontinuous yielding phenomenon
The deformation mechanism of titanium alloy at every stage during hot deformation was discussed, based on the characteristics of flow stress curves with discontinuous yielding. A viscoplastic constitutive model was built on the premise that the discontinuous yielding phenomenon was associated with the rapid dislocation multiplication at an early stage of yielding and the unified viscoplastic theory. In this model, the effect of deformation temperature and strain rate was considered. This model can describe the discontinuous yielding phenomenon, the slight degree of strain hardening after the low yield point and the mechanism of dynamic recrystallization when the strain achieved to the critical value where the dynamic recrystallization takes place. Applying the constitutive model to the isothermal compression of one new kind of metastable beta Ti2448 titanium alloy, the material constants in the model were identified by the GA-based global optimization method which was adopted in this paper. The relative difference between the predicted and experimental values is less than 5%, which implies that this constitutive model with high prediction based on the internal state variables can not only offer clear physical insight, but also can describe the flow behaviors of Ti2448 titanium alloy during hot deformation with discontinuous yielding. The generality of this model makes it possible to extend the theory to other titanium alloys that have discontinuous yielding phenomenon
2013, 42(1):64-69.
Abstract:
Ti0.10Zr0.15V0.35Cr0.10Ni0.30 + 1% La0.85Mg0.25Ni4.5Co0.35Al0.15 (mass fraction) composite hydrogen storage alloy was prepared by two-step arc melting. Results of XRD and SEM-EDS show that the main phase of the composite alloy is composed of V-based solid solution phase with bcc structure and C14 Laves phase with hexagonal structure. Electrochemical studies show that distinct synergetic effect appears during the composite process. P-C-T properties, activation performance, maximum discharge capacity, cyclic stability, low temperature dischargeability and high rate dischargeability of the composite alloy are significantly improved. Comparing with the matrix alloy, the composite alloy electrode has smaller charge-transfer resistance, higher exchange current density and bigger hydrogen diffusion coefficient, which seems to be related to formation of the secondary phase
Ti0.10Zr0.15V0.35Cr0.10Ni0.30 + 1% La0.85Mg0.25Ni4.5Co0.35Al0.15 (mass fraction) composite hydrogen storage alloy was prepared by two-step arc melting. Results of XRD and SEM-EDS show that the main phase of the composite alloy is composed of V-based solid solution phase with bcc structure and C14 Laves phase with hexagonal structure. Electrochemical studies show that distinct synergetic effect appears during the composite process. P-C-T properties, activation performance, maximum discharge capacity, cyclic stability, low temperature dischargeability and high rate dischargeability of the composite alloy are significantly improved. Comparing with the matrix alloy, the composite alloy electrode has smaller charge-transfer resistance, higher exchange current density and bigger hydrogen diffusion coefficient, which seems to be related to formation of the secondary phase
2013, 42(1):70-74.
Abstract:
Based on the software ABAQUS Explicit/Standard modules, three-dimensional finite element model of Ni-Cr-W-Mo superalloy workpiece with strange shape was built. On the basis of orthogonal test, the process parameters of the first pass were optimized, and the distribution of stress and the hot spinning regular pattern in the process of metal forming and springback were analyzed. The results show that the rotary velocity of mandrel has the most significant influence on breakage tendency, and the roller roundness radius on wrinkle tendency. After the unloading course the springback has a little effect on the trend of distribution of equivalent stress, and the most of the regional stress has been released. After the process of hot spinning, there is some deviation between the actual thickness and theoretical thickness value
Based on the software ABAQUS Explicit/Standard modules, three-dimensional finite element model of Ni-Cr-W-Mo superalloy workpiece with strange shape was built. On the basis of orthogonal test, the process parameters of the first pass were optimized, and the distribution of stress and the hot spinning regular pattern in the process of metal forming and springback were analyzed. The results show that the rotary velocity of mandrel has the most significant influence on breakage tendency, and the roller roundness radius on wrinkle tendency. After the unloading course the springback has a little effect on the trend of distribution of equivalent stress, and the most of the regional stress has been released. After the process of hot spinning, there is some deviation between the actual thickness and theoretical thickness value
2013, 42(1):75-79.
Abstract:
Novel Co-Al-W superalloy is a novel Co-base superalloy, with the precipitation strengthening by a ternary compound γ′-Co3(Al,W) phase on γ-Co matrix. The effect of alloying element Mo, Nb, Ta and Ti on friction and wear performance of Co-Al-W superalloys at room temperature was studied by THT07-135 type friction and wear tester and SEM, and cobalt-based Stellite 6 alloy was employed for comparison. Results show that the friction coefficient of 9.8W superalloy is smaller than that of cobalt-based Stellite 6. Alloying elements Mo, Nb and Ti can moderately reduce wear mass loss and friction coefficient of 9.8W superalloy, and improve the wear resistance. The Mo, Ti and Nb elements can clearly improve the wear resistance of 9.8W superalloy while the effect of Ta element is not obvious. The wear mechanism of Co-Al-W superalloy is mainly oxidation and abrasive wear, while that of Stellite 6 alloy mainly is delamination and abrasive wear.
Novel Co-Al-W superalloy is a novel Co-base superalloy, with the precipitation strengthening by a ternary compound γ′-Co3(Al,W) phase on γ-Co matrix. The effect of alloying element Mo, Nb, Ta and Ti on friction and wear performance of Co-Al-W superalloys at room temperature was studied by THT07-135 type friction and wear tester and SEM, and cobalt-based Stellite 6 alloy was employed for comparison. Results show that the friction coefficient of 9.8W superalloy is smaller than that of cobalt-based Stellite 6. Alloying elements Mo, Nb and Ti can moderately reduce wear mass loss and friction coefficient of 9.8W superalloy, and improve the wear resistance. The Mo, Ti and Nb elements can clearly improve the wear resistance of 9.8W superalloy while the effect of Ta element is not obvious. The wear mechanism of Co-Al-W superalloy is mainly oxidation and abrasive wear, while that of Stellite 6 alloy mainly is delamination and abrasive wear.
2013, 42(1):80-83.
Abstract:
High purity tungsten shaped charge liners (SCL) were prepared by chemical vapor deposition (CVD). In order to study the deformation mechanism of pure tungsten under explosion loading condition, the pure tungsten SCL were subjected to static penetration experiments. The microstructure features of retrieved slug were systematically investigated. Results show that the different areas of the retrieved slug show obviously different microstructure features due to different plastic deformation. Through analyzing the microstructure evolution of different areas of the retrieved slug, it can be concluded that the deformation mechanism of pure tungsten subjected to explosion loading is subgrain rotation dynamic recrystallization mechanism (RDR). No twinning deformation was observed. In addition, the original orientation of the CVD columnar grains has no obvious influence on deformation mechanism of pure tungsten under explosion loading conditions
High purity tungsten shaped charge liners (SCL) were prepared by chemical vapor deposition (CVD). In order to study the deformation mechanism of pure tungsten under explosion loading condition, the pure tungsten SCL were subjected to static penetration experiments. The microstructure features of retrieved slug were systematically investigated. Results show that the different areas of the retrieved slug show obviously different microstructure features due to different plastic deformation. Through analyzing the microstructure evolution of different areas of the retrieved slug, it can be concluded that the deformation mechanism of pure tungsten subjected to explosion loading is subgrain rotation dynamic recrystallization mechanism (RDR). No twinning deformation was observed. In addition, the original orientation of the CVD columnar grains has no obvious influence on deformation mechanism of pure tungsten under explosion loading conditions
2013, 42(1):84-88.
Abstract:
The effect of hot extrusion and aging treatment on microstructure and mechanical property of Mg-6Zn-1Zr-1.5Y alloy was investigated and the strengthening mechanism was clarified. The elongation increased and the strength first increased and then decreased with increasing extrusion ratio. Mg3Y2Zn3 phase precipitated during hot extrusion and the dislocation density decreased during aging treatment. The strength and elongation of the extrusion bar (λ=10) decreased, the strength and elongation of the extrusion bar (λ=13) increased, and the strength increased and the elongation decreased of the extrusion bar (λ=25). The major strengthening mechanism is aging strengthening, strain-hardening and Hall-petch strengthening. The mechanical property depended on Hall-petch strengthening and strain-hardening after hot extrusion, and depended on aging strengthening and strain-hardening after aging treatment
The effect of hot extrusion and aging treatment on microstructure and mechanical property of Mg-6Zn-1Zr-1.5Y alloy was investigated and the strengthening mechanism was clarified. The elongation increased and the strength first increased and then decreased with increasing extrusion ratio. Mg3Y2Zn3 phase precipitated during hot extrusion and the dislocation density decreased during aging treatment. The strength and elongation of the extrusion bar (λ=10) decreased, the strength and elongation of the extrusion bar (λ=13) increased, and the strength increased and the elongation decreased of the extrusion bar (λ=25). The major strengthening mechanism is aging strengthening, strain-hardening and Hall-petch strengthening. The mechanical property depended on Hall-petch strengthening and strain-hardening after hot extrusion, and depended on aging strengthening and strain-hardening after aging treatment
Cui Chongliang
,
Liu Xuhe
,
Wu Libin
,
Wu Ruizhi
,
Zhang Minlin
,
Qu Zhikun
,
Zhu Jiajun
,
Wang Chunfeng
2013, 42(1):89-93.
Abstract:
The microstructure and mechanical properties of as-extruded Mg-5Li-3Al-2Zn-xY alloy were investigated by optical microscope, scanning electron microscope, and X-ray diffraction. The results show that the grains of the alloy were refined due to the dynamic recrystallization, and the AlLi phases were broken and distributed along the extrusion direction during the extrusion process. The AlLi phase disappeared when the Y content increased to 2.0wt%. The highest tensile strength of the alloy reaches 326.3MPa after extrusion. Fine grain strengthening and secondary phase strengthening are the two dominant factors for improving the ultimate strength of the alloy. The effect of secondary phase strengthening is determined by the content, size and distribution of Al2Y
The microstructure and mechanical properties of as-extruded Mg-5Li-3Al-2Zn-xY alloy were investigated by optical microscope, scanning electron microscope, and X-ray diffraction. The results show that the grains of the alloy were refined due to the dynamic recrystallization, and the AlLi phases were broken and distributed along the extrusion direction during the extrusion process. The AlLi phase disappeared when the Y content increased to 2.0wt%. The highest tensile strength of the alloy reaches 326.3MPa after extrusion. Fine grain strengthening and secondary phase strengthening are the two dominant factors for improving the ultimate strength of the alloy. The effect of secondary phase strengthening is determined by the content, size and distribution of Al2Y
2013, 42(1):94-98.
Abstract:
Mg-8.5Li-3Al-xCe (x=0, 1, 3) alloys were prepared with vacuum induction melting method. Then the aging behavior of the Mg-8.5Li-3Al-xCe alloy was investigated. The results show that Ce has an obvious effect on the aging-hardening process. With the increase of Ce content, the aging hardness increases and the over-aging softening is suppressed to some extent. The aging hardness increase and the over-aging softening decrease of Mg-8.5Li-3Al-xCe (x=0, 1, 3) alloys is mainly attributed to that Ce inhibits the generation of age-hardening phase MgLi2A1 and over-aging softening phase AlLi. Ce can hinder the over-aging process in Mg-Li-Al alloys
Mg-8.5Li-3Al-xCe (x=0, 1, 3) alloys were prepared with vacuum induction melting method. Then the aging behavior of the Mg-8.5Li-3Al-xCe alloy was investigated. The results show that Ce has an obvious effect on the aging-hardening process. With the increase of Ce content, the aging hardness increases and the over-aging softening is suppressed to some extent. The aging hardness increase and the over-aging softening decrease of Mg-8.5Li-3Al-xCe (x=0, 1, 3) alloys is mainly attributed to that Ce inhibits the generation of age-hardening phase MgLi2A1 and over-aging softening phase AlLi. Ce can hinder the over-aging process in Mg-Li-Al alloys
2013, 42(1):99-103.
Abstract:
The effects of Sb on microstructure and mechanical properties of AM50-Y magnesium alloys have been studied. The results show that after Sb is added into the AM50-Y alloy, the grains are refined obviously and a few dispersed?phases YSb are formed, which promote the formation of fine, dispersed?Al2Y particles by providing the nucleation sites. With increasing of Sb content, the tensile strength and elongation at room temperature and at 150 °C, and the impact toughness at room temperature of the alloys increase first, and then decrease. When the content of Sb is up to 0.6%, the tensile strength, elongation and impact toughness at room temperature reach their maxima simultaneously of 257 MPa, 9.9% and 26 J·cm-2, increased by 13.7%, 15.9% and 14.9% respectively compared with the alloy without Sb addition. Meanwhile, the tensile strength and elongation at 150 °C reach their maxima of 203 MPa and 11.9%, increased by 12.8% and 15.5% respectively, showing the best combined mechanical properties
The effects of Sb on microstructure and mechanical properties of AM50-Y magnesium alloys have been studied. The results show that after Sb is added into the AM50-Y alloy, the grains are refined obviously and a few dispersed?phases YSb are formed, which promote the formation of fine, dispersed?Al2Y particles by providing the nucleation sites. With increasing of Sb content, the tensile strength and elongation at room temperature and at 150 °C, and the impact toughness at room temperature of the alloys increase first, and then decrease. When the content of Sb is up to 0.6%, the tensile strength, elongation and impact toughness at room temperature reach their maxima simultaneously of 257 MPa, 9.9% and 26 J·cm-2, increased by 13.7%, 15.9% and 14.9% respectively compared with the alloy without Sb addition. Meanwhile, the tensile strength and elongation at 150 °C reach their maxima of 203 MPa and 11.9%, increased by 12.8% and 15.5% respectively, showing the best combined mechanical properties
2013, 42(1):104-108.
Abstract:
The electron-beam welded microstructure of spray formed Al-Zn-Mg-Cu alloy was investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy etc. The results indicate that the welds are composed of three zones, the base metal, nugget and heat affected zone. The width of the weld is 0.3~1 mm, and the weld nugget zone is composed of equiaxed grains with an average grain size of 3~8 μm, and the second phases are mainly distributed along the grain boundaries. Heat-affected zone is composed of α (Al) and Al/AlZnMgCu eutectic structure. Some of the heat affected zone have displayed remelting characteristics. After T6 treatment, most of the AlZnMgCu phases in weld nugget were dissolved into α (Al), and the eutectic structure in heat-affected zone disappeared
The electron-beam welded microstructure of spray formed Al-Zn-Mg-Cu alloy was investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy etc. The results indicate that the welds are composed of three zones, the base metal, nugget and heat affected zone. The width of the weld is 0.3~1 mm, and the weld nugget zone is composed of equiaxed grains with an average grain size of 3~8 μm, and the second phases are mainly distributed along the grain boundaries. Heat-affected zone is composed of α (Al) and Al/AlZnMgCu eutectic structure. Some of the heat affected zone have displayed remelting characteristics. After T6 treatment, most of the AlZnMgCu phases in weld nugget were dissolved into α (Al), and the eutectic structure in heat-affected zone disappeared
2013, 42(1):109-113.
Abstract:
Vanadium films were fabricated on industrial pure aluminum using High Power Pulsed Magnetron Sputtering (HPPMS). The influences of DC bias on phase structure, surface morphology, and especially the corrosion resistance of vanadium films after annealed at different temperatures have been investigated. XRD patterns show the highest intensity of V(111) preferential orientation. The surface of vanadium films was smooth and flat with a maximum roughness of 0.488 nm. The surface roughness decreased with increasing bias and increased if the bias further increased. The deposition rate decreased and increased with increasing sample bias. The reason is that ion attracting effect and sputtering effect competed in the deposition process. The sample treated at –100 V possessed the best corrosion resistance with the corrosion potential increased by 0.425 V and the corrosion current decreased by two orders of magnitude compared with the substrate. The samples exhibited much better corrosion resistance after annealing. The corrosion current of the samples annealed at 200 °C decreased by an order of magnitude compared with the substrate. The corrosion resistance of vanadium films increased less obviously compared with the substrate after annealing at 300 °C
Vanadium films were fabricated on industrial pure aluminum using High Power Pulsed Magnetron Sputtering (HPPMS). The influences of DC bias on phase structure, surface morphology, and especially the corrosion resistance of vanadium films after annealed at different temperatures have been investigated. XRD patterns show the highest intensity of V(111) preferential orientation. The surface of vanadium films was smooth and flat with a maximum roughness of 0.488 nm. The surface roughness decreased with increasing bias and increased if the bias further increased. The deposition rate decreased and increased with increasing sample bias. The reason is that ion attracting effect and sputtering effect competed in the deposition process. The sample treated at –100 V possessed the best corrosion resistance with the corrosion potential increased by 0.425 V and the corrosion current decreased by two orders of magnitude compared with the substrate. The samples exhibited much better corrosion resistance after annealing. The corrosion current of the samples annealed at 200 °C decreased by an order of magnitude compared with the substrate. The corrosion resistance of vanadium films increased less obviously compared with the substrate after annealing at 300 °C
2013, 42(1):114-119.
Abstract:
Mg-Zn-Mn alloy ZM71 with different additions of Ce element was hot extruded and then was heat-treated. Tensile mechanical properties at room temperature of different states ZM71 and ZM71-xCe alloys were also tested. Microstructure observations under different states were performed by means of optical microscopy (OM), X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM), differential thermal analysis (DSC), energy spectrum analysis (EDS), and transmission electron microscopy (TEM). The existence form and acting mechanism of Ce elements in ZM71 alloy and the influence of Ce content on microstructure and mechanical properties of ZM71 alloy were investigated. The results show that a ternary τ phase was identified in ZM71-xCe alloys, which distributed at grain boundaries and interdendritic, and refined the microstructure of as-cast alloys. Ce element had an obvious effect on refining the microstructure of as-extruded alloys by restricting the occurrence of dynamic recrystallization and restraining the grain growth during extrusion and improved the mechanical properties, but the Ce addition should be no more than 1%. ZM71-0.5Ce alloy had better overall mechanical properties, with σb =318 MPa, σ0.2=250 MPa and δ=13.6%. Solution and aging was not available for improving mechanical properties of as-extruded Mg-Zn-Mn-Ce with high Zn content
Mg-Zn-Mn alloy ZM71 with different additions of Ce element was hot extruded and then was heat-treated. Tensile mechanical properties at room temperature of different states ZM71 and ZM71-xCe alloys were also tested. Microstructure observations under different states were performed by means of optical microscopy (OM), X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM), differential thermal analysis (DSC), energy spectrum analysis (EDS), and transmission electron microscopy (TEM). The existence form and acting mechanism of Ce elements in ZM71 alloy and the influence of Ce content on microstructure and mechanical properties of ZM71 alloy were investigated. The results show that a ternary τ phase was identified in ZM71-xCe alloys, which distributed at grain boundaries and interdendritic, and refined the microstructure of as-cast alloys. Ce element had an obvious effect on refining the microstructure of as-extruded alloys by restricting the occurrence of dynamic recrystallization and restraining the grain growth during extrusion and improved the mechanical properties, but the Ce addition should be no more than 1%. ZM71-0.5Ce alloy had better overall mechanical properties, with σb =318 MPa, σ0.2=250 MPa and δ=13.6%. Solution and aging was not available for improving mechanical properties of as-extruded Mg-Zn-Mn-Ce with high Zn content
2013, 42(1):120-125.
Abstract:
2519A aluminum alloys with different Ce contents were investigated with the true stress-strain curves at different temperatures of 293 and 573 K and different nominal strain rates of 1200, 3100 and 5100 s-1 in dynamic impact testing by split Hopkinson pressure bar (SHPB). The microstructures of the impacted samples were observed by transmission electron microscopy (TEM) to examine the precipitated phase evolution and the interaction mechanism of heat-resistant phase at adiabatic temperature. The results indicate that the absorbing ability of the alloy with 0.2% Ce is the highest in the alloys with 0% Ce, 0.2% Ce and 0.4% Ce, and the impact resistance is the best. The yield strength reaches 614 MPa at 3100 s-1, 293 K and it decreases at 573 K. With increasing the strain rate, the hardness of different alloys decreases, the volume fraction of θ′ decreases and the growth and coarsening of θ′ become obvious. The transformation of θ′ into θ occurred, and the transformation rate is the slowest for the alloy with 0.2% Ce
2519A aluminum alloys with different Ce contents were investigated with the true stress-strain curves at different temperatures of 293 and 573 K and different nominal strain rates of 1200, 3100 and 5100 s-1 in dynamic impact testing by split Hopkinson pressure bar (SHPB). The microstructures of the impacted samples were observed by transmission electron microscopy (TEM) to examine the precipitated phase evolution and the interaction mechanism of heat-resistant phase at adiabatic temperature. The results indicate that the absorbing ability of the alloy with 0.2% Ce is the highest in the alloys with 0% Ce, 0.2% Ce and 0.4% Ce, and the impact resistance is the best. The yield strength reaches 614 MPa at 3100 s-1, 293 K and it decreases at 573 K. With increasing the strain rate, the hardness of different alloys decreases, the volume fraction of θ′ decreases and the growth and coarsening of θ′ become obvious. The transformation of θ′ into θ occurred, and the transformation rate is the slowest for the alloy with 0.2% Ce
2013, 42(1):126-130.
Abstract:
The phase component and surface structure of ITO sputtering target materials fabricated by hot pressing method were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The results indicate that the peaks of XRD pattern were shifted, which can be explained to the great difference of ion radius between the solute and the solvent. On the other hand, the peak shift of core level in X-ray photoelectron spectrum was due to the increasing occupancy of the ITO conduction band and the increase of Fermi level when Sn was doped. The research is beneficial to fabricate ITO sputtering target material with homogeneous composition and structure and high density
The phase component and surface structure of ITO sputtering target materials fabricated by hot pressing method were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The results indicate that the peaks of XRD pattern were shifted, which can be explained to the great difference of ion radius between the solute and the solvent. On the other hand, the peak shift of core level in X-ray photoelectron spectrum was due to the increasing occupancy of the ITO conduction band and the increase of Fermi level when Sn was doped. The research is beneficial to fabricate ITO sputtering target material with homogeneous composition and structure and high density
26 Influence Investigation of Temperature on Thermal Contact Conductance across GH4169/K417 Interface
2013, 42(1):131-134.
Abstract:
Using self-developed thermal contact conductance testing equipment with compensation heater, the thermal contact conductance of aero engine high-temperature structure material GH4169/K417 with different temperatures(160 ~ 280 °C) and roughness were tested, the influence behavior of the temperature on the thermal contact conductance was studied, and the thermal contact conductance test results under the condition with and without compensation heater were comparatively anglicized. Results show that the thermal contact conductance testing equipment with compensation heater can effectively reduce the lateral heat loss, and gradually with the rise of temperature effect is obvious. To different roughness of GH4169/K417 material combination, influence of temperature on the thermal contact conductance is different, which is mainly related to the deformation and oxidation between the relevant materials interface
Using self-developed thermal contact conductance testing equipment with compensation heater, the thermal contact conductance of aero engine high-temperature structure material GH4169/K417 with different temperatures(160 ~ 280 °C) and roughness were tested, the influence behavior of the temperature on the thermal contact conductance was studied, and the thermal contact conductance test results under the condition with and without compensation heater were comparatively anglicized. Results show that the thermal contact conductance testing equipment with compensation heater can effectively reduce the lateral heat loss, and gradually with the rise of temperature effect is obvious. To different roughness of GH4169/K417 material combination, influence of temperature on the thermal contact conductance is different, which is mainly related to the deformation and oxidation between the relevant materials interface
2013, 42(1):135-139.
Abstract:
Coating formation on multi-walled carbon nanotubes (MWCNTs) treated in a coke bed in the temperature range of 1000~1500 °C using silicon powder (Si) and the mixture of aluminum and silicon powders (Al+Si) as the silicon sources and its oxidation resistance were investigated by means of X-ray diffraction, high resolution transmission electron microscopy equipped with energy dispersive X-ray spectroscopy and thermogravimetric analysis-differential scanning calorimetry. Results show that using Si as a silicon source, SiC coating forms on the surface of MWCNTs after treated below 1400 °C. At 1500 °C, most of MWCNTs have transformed into solid SiC nanowires. Using Al+Si as a silicon source, the thickness of the coating increases at the same treated temperature compared with Si source. In addition, transformation of MWCNTs is prevented after treated at 1500 °C. The oxidation resistance of the treated MWCNTs improves compared with the as-received ones, and it gets better with increasing the thickness of the coating. Non-isothermal kinetics shows that oxidation activation energy of the as-received MWCNTs is 157.69 kJ/mol, while they are 202.39 kJ/mol and 230.70 kJ/mol after MWCNTs treated at 1400 °C using Si and Al+Si as the silicon sources, respectively
Coating formation on multi-walled carbon nanotubes (MWCNTs) treated in a coke bed in the temperature range of 1000~1500 °C using silicon powder (Si) and the mixture of aluminum and silicon powders (Al+Si) as the silicon sources and its oxidation resistance were investigated by means of X-ray diffraction, high resolution transmission electron microscopy equipped with energy dispersive X-ray spectroscopy and thermogravimetric analysis-differential scanning calorimetry. Results show that using Si as a silicon source, SiC coating forms on the surface of MWCNTs after treated below 1400 °C. At 1500 °C, most of MWCNTs have transformed into solid SiC nanowires. Using Al+Si as a silicon source, the thickness of the coating increases at the same treated temperature compared with Si source. In addition, transformation of MWCNTs is prevented after treated at 1500 °C. The oxidation resistance of the treated MWCNTs improves compared with the as-received ones, and it gets better with increasing the thickness of the coating. Non-isothermal kinetics shows that oxidation activation energy of the as-received MWCNTs is 157.69 kJ/mol, while they are 202.39 kJ/mol and 230.70 kJ/mol after MWCNTs treated at 1400 °C using Si and Al+Si as the silicon sources, respectively
2013, 42(1):140-144.
Abstract:
The La0.7Sr0.3MnO3 and ZnO deposition films prepared by the pulse laser deposition on LAO (100) substrates were investigated. The sample with different doped concentrations led to interaction between electron spins and orbital order, as well as short-range polaronic disorder. XRD patterns found that La1-xSrxMnO3 and ZnO diffraction peak had (100), (200) and (002) dominant orientations. The multilayers films lattices were matched with each other. The V-I properties and R-T curves show the heterojunction have half-metal optoelectronic conductivity properties. We measured the photoresistances and MR of LAO/La0.7Sr0.3MnO3/ZnO heterojunction in the optical and magnetic field respectively. The results indicate that the La0.7Sr0.3MnO3 layer with x=0.3~0.4 exhibited the metal to insulator transition at Tp 250 K and paramagnetic to antiferromagnetic phase transition at Tc 175 K. The La0.7Sr0.3MnO3/ZnO heterojunction realized quantum energy band clipping and rebuilt the energy band structure. The photoresistance with irradiation of pulsed and CW laser below Tp 220 K are increased. The results show that the changes of spin orientation, barriers concentration, state density and spin-orbit interactions led to photoresistance. The polarization and interface strain between La0.7Sr0.3MnO3 and ZnO heterojunction occurred related with defect structure at dissipation layer interface
The La0.7Sr0.3MnO3 and ZnO deposition films prepared by the pulse laser deposition on LAO (100) substrates were investigated. The sample with different doped concentrations led to interaction between electron spins and orbital order, as well as short-range polaronic disorder. XRD patterns found that La1-xSrxMnO3 and ZnO diffraction peak had (100), (200) and (002) dominant orientations. The multilayers films lattices were matched with each other. The V-I properties and R-T curves show the heterojunction have half-metal optoelectronic conductivity properties. We measured the photoresistances and MR of LAO/La0.7Sr0.3MnO3/ZnO heterojunction in the optical and magnetic field respectively. The results indicate that the La0.7Sr0.3MnO3 layer with x=0.3~0.4 exhibited the metal to insulator transition at Tp 250 K and paramagnetic to antiferromagnetic phase transition at Tc 175 K. The La0.7Sr0.3MnO3/ZnO heterojunction realized quantum energy band clipping and rebuilt the energy band structure. The photoresistance with irradiation of pulsed and CW laser below Tp 220 K are increased. The results show that the changes of spin orientation, barriers concentration, state density and spin-orbit interactions led to photoresistance. The polarization and interface strain between La0.7Sr0.3MnO3 and ZnO heterojunction occurred related with defect structure at dissipation layer interface
2013, 42(1):145-148.
Abstract:
With sufficient investigating the effect of pre-oxidation, sealing temperature and holding time on the shear strength and microstructure of the Al2O3-Nb sealing materials. The shear strength, microstructure and element distribution of sealing material were investigated by the strength machine, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Furthermore, the X-ray diffraction (XRD) was used to investigate the phase of sealing region. The strength results showed that the shear strength reached to 94.5 MPa when the sealing temperature was 1390 ℃ and holding 10 min, the XRD results showed that the Dy2Si2O7 phase was found in the sealant/Al2O3 interface. In addition, the thickness of reaction layer which was formed near the interface of sealant/Al2O3 was about 2 μm
With sufficient investigating the effect of pre-oxidation, sealing temperature and holding time on the shear strength and microstructure of the Al2O3-Nb sealing materials. The shear strength, microstructure and element distribution of sealing material were investigated by the strength machine, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Furthermore, the X-ray diffraction (XRD) was used to investigate the phase of sealing region. The strength results showed that the shear strength reached to 94.5 MPa when the sealing temperature was 1390 ℃ and holding 10 min, the XRD results showed that the Dy2Si2O7 phase was found in the sealant/Al2O3 interface. In addition, the thickness of reaction layer which was formed near the interface of sealant/Al2O3 was about 2 μm
30 Study on Arc Erosion Resistance Properties of Nano-AgSnO2 Electrical Contact Materials Doped with Bi
2013, 42(1):149-152.
Abstract:
The Bi-doped nanocomposite AgSnO2 contact alloys were prepared by sol-gel method and breaking arc experiments were carried out. The morphology of the arc erosion, arc energy and arc duration of AgSnO2 contact alloys was observed and investigated by means of Scanning Electron Microscopy (SEM). Results show that the addition of Bi element improves the wettability of Ag to SnO2 and prevents the temperature arising owing to the formation of SnO2 insulation layer and thus significantly improves the electrical properties, such as the electrical life, anti-fusion welding ability, and electrical arc resistance of the materials
The Bi-doped nanocomposite AgSnO2 contact alloys were prepared by sol-gel method and breaking arc experiments were carried out. The morphology of the arc erosion, arc energy and arc duration of AgSnO2 contact alloys was observed and investigated by means of Scanning Electron Microscopy (SEM). Results show that the addition of Bi element improves the wettability of Ag to SnO2 and prevents the temperature arising owing to the formation of SnO2 insulation layer and thus significantly improves the electrical properties, such as the electrical life, anti-fusion welding ability, and electrical arc resistance of the materials
2013, 42(1):153-157.
Abstract:
The microstructure and texture evolution of Zirconium tubes extruded at different temperatures have been investigated using X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) technology. The results show that dynamic recovery and recrystallization occurred in the hot-extruded tubes. The microstructure consists of sub-grains containing small angle boundary and equiaxed grains. The temperature has no effect on the mean size of equiaxed grains. However, there is wide difference in texture at different temperatures. The texture component of the tube extruded at 650 °C consists of fiber and {0001}, while the texture component is <>fiber and {0001}<> with more basal poles in the tangential direction for the tube extruded at 630 °C.
The microstructure and texture evolution of Zirconium tubes extruded at different temperatures have been investigated using X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) technology. The results show that dynamic recovery and recrystallization occurred in the hot-extruded tubes. The microstructure consists of sub-grains containing small angle boundary and equiaxed grains. The temperature has no effect on the mean size of equiaxed grains. However, there is wide difference in texture at different temperatures. The texture component of the tube extruded at 650 °C consists of fiber and {0001}, while the texture component is <>fiber and {0001}<> with more basal poles in the tangential direction for the tube extruded at 630 °C.
2013, 42(1):158-161.
Abstract:
Pack boronizing of titanium was conducted at 900 °C and holding for 6 h when B4C content in (B4C+ B2O3) was 30% and 40% respectively. Surfaces boride was characterized by X-ray diffraction (XRD). The results show that TiB2 is not found for both B4C contents. TiB is formed on titanium surfaces when the content of B4C in (B4C+B2O3) is 40% at 900 °C, while TiB is very little when the content of B4C in (B4C+B2O3) is 30% at the same temperature. The active B is mainly supplied by B4C. TiB2 is formed at titanium surfaces and the growth of TiB is inhibited as the B4C content is 40% at 1050 °C. Both TiB2 and TiB would be formed based on thermodynamics. TiB is mainly formed at 900 °C because dynamically the diffusivity of B in TiB is higher than that in TiB2, while TiB2 is mainly formed at 1050 °C because the diffusivity of B in Ti is higher than that in TiB
Pack boronizing of titanium was conducted at 900 °C and holding for 6 h when B4C content in (B4C+ B2O3) was 30% and 40% respectively. Surfaces boride was characterized by X-ray diffraction (XRD). The results show that TiB2 is not found for both B4C contents. TiB is formed on titanium surfaces when the content of B4C in (B4C+B2O3) is 40% at 900 °C, while TiB is very little when the content of B4C in (B4C+B2O3) is 30% at the same temperature. The active B is mainly supplied by B4C. TiB2 is formed at titanium surfaces and the growth of TiB is inhibited as the B4C content is 40% at 1050 °C. Both TiB2 and TiB would be formed based on thermodynamics. TiB is mainly formed at 900 °C because dynamically the diffusivity of B in TiB is higher than that in TiB2, while TiB2 is mainly formed at 1050 °C because the diffusivity of B in Ti is higher than that in TiB
2013, 42(1):162-165.
Abstract:
The monolithic foamed gold was synthesized by a template deposit-dealloying method with polystyrene (PS) template and gold silver electroless depositing and dealloying. The results indicate that the deposited gold has the thickness of 70~90 nm, and the deposited Au/Ag has the thickness of 200~400 nm after silver electroless depositing on the surface of Au/PS. The self-supported hollow spheres Au40Ag60 alloy was obtained after the template removed. The ultra-low-density gold monoliths with multimodal pore structure, hollow spheres of about 10 μm, and density of 0.8 g/cm3 was obtained after dealloying heat treatment
The monolithic foamed gold was synthesized by a template deposit-dealloying method with polystyrene (PS) template and gold silver electroless depositing and dealloying. The results indicate that the deposited gold has the thickness of 70~90 nm, and the deposited Au/Ag has the thickness of 200~400 nm after silver electroless depositing on the surface of Au/PS. The self-supported hollow spheres Au40Ag60 alloy was obtained after the template removed. The ultra-low-density gold monoliths with multimodal pore structure, hollow spheres of about 10 μm, and density of 0.8 g/cm3 was obtained after dealloying heat treatment
2013, 42(1):166-170.
Abstract:
By producing TA18 experimental tubes with different dimension, the effects of Q value, accumulated deformation rate and annealing temperature on the microstructure and mechanical properties of the finished tubes were studied. Results show that the tubes can be rolled successfully in two-roll mill without cracking in surface, when the deformation rate is under 55% and the Q value maintains 0.53~1.14. With the increase of the deformation rate, the strength of the experimental tubes rises gradually while the elongation falls. However, the influence of the minor deformation rate on the elongation is very limited. In addition, the strength of the experimental tubes decreases and the elongation improves with the increase of the annealing temperature. Meanwhile, the work-hardening effect is diminished gradually. It is also found that the recrystallized grain size distribution of the experimental tubes would be non-homogeneous if the deformation rate is too low, which can result in the decrease of the elongation of the tubes annealed. After the process optimizing, the mechanical properties of TA18 experimental tubes can reach UTS=920 MPa, YS=755 MPa and El=14%.
By producing TA18 experimental tubes with different dimension, the effects of Q value, accumulated deformation rate and annealing temperature on the microstructure and mechanical properties of the finished tubes were studied. Results show that the tubes can be rolled successfully in two-roll mill without cracking in surface, when the deformation rate is under 55% and the Q value maintains 0.53~1.14. With the increase of the deformation rate, the strength of the experimental tubes rises gradually while the elongation falls. However, the influence of the minor deformation rate on the elongation is very limited. In addition, the strength of the experimental tubes decreases and the elongation improves with the increase of the annealing temperature. Meanwhile, the work-hardening effect is diminished gradually. It is also found that the recrystallized grain size distribution of the experimental tubes would be non-homogeneous if the deformation rate is too low, which can result in the decrease of the elongation of the tubes annealed. After the process optimizing, the mechanical properties of TA18 experimental tubes can reach UTS=920 MPa, YS=755 MPa and El=14%.
2013, 42(1):171-175.
Abstract:
Ti-Al amorphous composite coatings were prepared at room temperature on the Ti6Al4V (TC4) substrates surface by means of mechanical alloying (MA). XRD, SEM, EDS and micro hardness test technique were employed to investigate surface phase, cross-sectional microstructures and micro-hardness of the coatings. The results show that the coatings are formed via a combination of cold welding, deformation and fracture processes. The coating thickness increased first, then decreased and finally verged to a constant value with increase of milling time; the as-synthesized coatings showed structures with high apparent density and free of porosity. Ti-Al amorphous composite coating, ~200 μm thick, was obtained when rotation speed was 400 r/min and milling time was 12 h. Meanwhile, it was also found that the maximum hardness HV0.1 value of the coating achieved 5800 MPa, which was about threefold higher than that of the substrate. The volume content of the amorphous phase in the coating amounted to 49.53% and 96.35% analyzed by the calculation of the X-ray diffraction intensity curve information when milling time was 6 h and 12 h respectively.
Ti-Al amorphous composite coatings were prepared at room temperature on the Ti6Al4V (TC4) substrates surface by means of mechanical alloying (MA). XRD, SEM, EDS and micro hardness test technique were employed to investigate surface phase, cross-sectional microstructures and micro-hardness of the coatings. The results show that the coatings are formed via a combination of cold welding, deformation and fracture processes. The coating thickness increased first, then decreased and finally verged to a constant value with increase of milling time; the as-synthesized coatings showed structures with high apparent density and free of porosity. Ti-Al amorphous composite coating, ~200 μm thick, was obtained when rotation speed was 400 r/min and milling time was 12 h. Meanwhile, it was also found that the maximum hardness HV0.1 value of the coating achieved 5800 MPa, which was about threefold higher than that of the substrate. The volume content of the amorphous phase in the coating amounted to 49.53% and 96.35% analyzed by the calculation of the X-ray diffraction intensity curve information when milling time was 6 h and 12 h respectively.
2013, 42(1):176-179.
Abstract:
The MgCu2 Laves phase Mg(Cu1-xNix)2 (0≤x≤0.35) was prepared by means of mechanical activation combined with hot-pressed sintering. The phase, micromorphology and mechanical properties of hot-pressed products were analyzed. The results showe that although part of the Cu atoms in MgCu2 was substituted by Ni, the crystal structure was not changed, and the main phase was still the C15 structure (MgCu2 type) Laves phase. With the increase of Ni content, the diffraction peak shifted to the high angular position and the lattice constant gradually decreased; after adding Ni, metallurgical structure became more uniform and smaller. Lattice distortion and grain size increased and relative density increased too. At the same time, with the increase of Ni content, the hardness increased, and the relative density and the flexural strength increased first and then decreased
The MgCu2 Laves phase Mg(Cu1-xNix)2 (0≤x≤0.35) was prepared by means of mechanical activation combined with hot-pressed sintering. The phase, micromorphology and mechanical properties of hot-pressed products were analyzed. The results showe that although part of the Cu atoms in MgCu2 was substituted by Ni, the crystal structure was not changed, and the main phase was still the C15 structure (MgCu2 type) Laves phase. With the increase of Ni content, the diffraction peak shifted to the high angular position and the lattice constant gradually decreased; after adding Ni, metallurgical structure became more uniform and smaller. Lattice distortion and grain size increased and relative density increased too. At the same time, with the increase of Ni content, the hardness increased, and the relative density and the flexural strength increased first and then decreased
2013, 42(1):180-184.
Abstract:
Cu-Ni is one of good materials as a substrate for producing biaxially textured YBCO coating conductors. The non-magnetic CuNi alloy substrate was prepared by rolling assisted biaxially textured substrates (RABiTS) technology. The orientation as a function of annealing temperatures for the as-obtained CuNi substrate was characterized by XRD and EBSD. The results show that the heat treatment process is an important factor for the texture transition in CuNi alloy substrate. The percentage of the cube texture in CuNi alloy substrate obtained by the optimized heat treatment process is as high as 97.0% within a tolerance angle smaller than 10o. The optimized heat treatment process is holding the tape at 950 oC for 60 min
Cu-Ni is one of good materials as a substrate for producing biaxially textured YBCO coating conductors. The non-magnetic CuNi alloy substrate was prepared by rolling assisted biaxially textured substrates (RABiTS) technology. The orientation as a function of annealing temperatures for the as-obtained CuNi substrate was characterized by XRD and EBSD. The results show that the heat treatment process is an important factor for the texture transition in CuNi alloy substrate. The percentage of the cube texture in CuNi alloy substrate obtained by the optimized heat treatment process is as high as 97.0% within a tolerance angle smaller than 10o. The optimized heat treatment process is holding the tape at 950 oC for 60 min
2013, 42(1):185-189.
Abstract:
Lutetium oxide nanocrystals codoped with Yb3+ and Tm3+ were synthesized by the hydrothermal method. Effect of the pH values of precursor solutions on the structure, morphology and upconversion luminescent properties of the nanocrystals was investigated. XRD results show that all the nanocrystals can be indexed to pure cubic phase of Lu2O3 with good crystallinity. Blue and red emissions from the prepared nanocrystals are observed at 980 nm laser excitation, which are located at 490 nm and 653 nm, respectively. The upconversion emission intensity of Lu2O3:2%Yb3+, 0.2%Tm3+ nanocrystals prepared at pH=9 is the strongest. The enhancement of the upconversion luminescence is suggested to be the consequence of the decreased number of OH- groups and the enlarged nanocrystals size. Power-dependent investigation reveals that the blue (490 nm) and red (653 nm) upconversion luminescence is a three-photon upconversion process
Lutetium oxide nanocrystals codoped with Yb3+ and Tm3+ were synthesized by the hydrothermal method. Effect of the pH values of precursor solutions on the structure, morphology and upconversion luminescent properties of the nanocrystals was investigated. XRD results show that all the nanocrystals can be indexed to pure cubic phase of Lu2O3 with good crystallinity. Blue and red emissions from the prepared nanocrystals are observed at 980 nm laser excitation, which are located at 490 nm and 653 nm, respectively. The upconversion emission intensity of Lu2O3:2%Yb3+, 0.2%Tm3+ nanocrystals prepared at pH=9 is the strongest. The enhancement of the upconversion luminescence is suggested to be the consequence of the decreased number of OH- groups and the enlarged nanocrystals size. Power-dependent investigation reveals that the blue (490 nm) and red (653 nm) upconversion luminescence is a three-photon upconversion process
2013, 42(1):190-193.
Abstract:
The growth process of tantalum capacitor oxide film for 0603 size was investigated. The main process parameters of dielectric film Ta2O5 quality including formation fluid type, formation liquid concentration, current density and constant voltage time were employed to carry out experiments. At last DC leakage current of wet measure was collected, and through comparative experiments the best process parameters of the oxidation film growth were obtained. In conclusion, the best process parameters are 0.2% (volume ratio) nitric acid solution, 40 mA/g current density and 5 h constant voltage time. Through the best process parameters, the oxidation film quality can be improved greatly. Finally, leakage current is very small and comes to 0.036 μA
The growth process of tantalum capacitor oxide film for 0603 size was investigated. The main process parameters of dielectric film Ta2O5 quality including formation fluid type, formation liquid concentration, current density and constant voltage time were employed to carry out experiments. At last DC leakage current of wet measure was collected, and through comparative experiments the best process parameters of the oxidation film growth were obtained. In conclusion, the best process parameters are 0.2% (volume ratio) nitric acid solution, 40 mA/g current density and 5 h constant voltage time. Through the best process parameters, the oxidation film quality can be improved greatly. Finally, leakage current is very small and comes to 0.036 μA
2013, 42(1):194-199.
Abstract:
The effects of sintering temperature (Tsps) on the magnetic properties and density of NdFeB magnets prepared by spark plasma sintering (SPS) from HDDR powders were studied. With increasing the sintering temperature in the range of 650-900 °C, the remanence (Br), intrinsic coercivity (Hcj) and maximum energy product ((BH)max) all increased first and then decreased. The optimum magnetic properties of Br = 0.78 T, Hcj = 577 kA/m and (BH)max = 78 kJ/m3 were obtained in the samples SPSed at 800 °C and the density reached 99% of the theoretical. The microstructure, XRD patterns and magnetic properties indicated that the sample (Tsps = 800 °C) was anisotropic to a certain degree. But the grain growth was obvious when the Tsps reached 900 °C. The SPSed magnet with optimal magnetic properties was subjected to hot deformation at 800 °C and an anisotropic magnet was obtained. The hot deformation made the Nd2Fe14B grain orient in such a way that the c-axis of the Nd2Fe14B grain was parallel to the pressing direction. However, the alignment of grains was disrupted by a small amount of abnormal large grains. The magnetic properties parallel to the c-axis of the SPSed + HDed magnet were as follows: Br = 1.09 T, Hcj = 384 kA/m, and (BH)max = 114 kJ/m3
The effects of sintering temperature (Tsps) on the magnetic properties and density of NdFeB magnets prepared by spark plasma sintering (SPS) from HDDR powders were studied. With increasing the sintering temperature in the range of 650-900 °C, the remanence (Br), intrinsic coercivity (Hcj) and maximum energy product ((BH)max) all increased first and then decreased. The optimum magnetic properties of Br = 0.78 T, Hcj = 577 kA/m and (BH)max = 78 kJ/m3 were obtained in the samples SPSed at 800 °C and the density reached 99% of the theoretical. The microstructure, XRD patterns and magnetic properties indicated that the sample (Tsps = 800 °C) was anisotropic to a certain degree. But the grain growth was obvious when the Tsps reached 900 °C. The SPSed magnet with optimal magnetic properties was subjected to hot deformation at 800 °C and an anisotropic magnet was obtained. The hot deformation made the Nd2Fe14B grain orient in such a way that the c-axis of the Nd2Fe14B grain was parallel to the pressing direction. However, the alignment of grains was disrupted by a small amount of abnormal large grains. The magnetic properties parallel to the c-axis of the SPSed + HDed magnet were as follows: Br = 1.09 T, Hcj = 384 kA/m, and (BH)max = 114 kJ/m3
2013, 42(1):200-203.
Abstract:
The Fe2O3/Ag core-shell composite nanoparticles were prepared via a simple method at low temperature. The structure of Ag-Fe2O3 core-shell composite nanoparticles was confirmed by XRD, TEM and UV spectra. The results show that the size distributions of the Ag nanocomposites averaged 35 nm, with a thickness of 7.5 nm or 15 nm of Ag layer. Magnetic measurements show that the composite nanoparticles exhibited a typical ferromagnetic behavior, a specific saturation magnetization of 0.98 (A·m2)·kg-1 and an intrinsic coercivity of 8.48×103 A/m at room temperature. The electric conductivity of Fe2O3/Ag core-shell composite nanoparticles is up to 0.62 S/cm. Through this method can obtain higher yield of Fe2O3/Ag core-shell composite nanoparticles, and this method also can control the size and composite particle dispersion easily. It will have a broad application prospects in catalyst, medicine, photoelectric etc
The Fe2O3/Ag core-shell composite nanoparticles were prepared via a simple method at low temperature. The structure of Ag-Fe2O3 core-shell composite nanoparticles was confirmed by XRD, TEM and UV spectra. The results show that the size distributions of the Ag nanocomposites averaged 35 nm, with a thickness of 7.5 nm or 15 nm of Ag layer. Magnetic measurements show that the composite nanoparticles exhibited a typical ferromagnetic behavior, a specific saturation magnetization of 0.98 (A·m2)·kg-1 and an intrinsic coercivity of 8.48×103 A/m at room temperature. The electric conductivity of Fe2O3/Ag core-shell composite nanoparticles is up to 0.62 S/cm. Through this method can obtain higher yield of Fe2O3/Ag core-shell composite nanoparticles, and this method also can control the size and composite particle dispersion easily. It will have a broad application prospects in catalyst, medicine, photoelectric etc
2013, 42(1):204-210.
Abstract:
To improve the corrosive-wear resistance of the Ti6Al4V titanium alloy, W-Mo co-penetrated layer was prepared on Ti6Al4V titanium alloy surface by double glow discharge technique. The corrosive-wear properties of the co-penetrated layer were investigated. The results show that W-Mo co-penetrated layer combined well with the substrate, and the layer was composed of deposited layer, transition layer and diffused layer. Compared with Ti6Al4V substrate, the alloying layer exhibited a lower friction coefficient, improved wear morphology and an obviously decreased wearing volume in 5wt%NaCl and 5wt% H2SO4 solutions. All these indicate that W-Mo co-penetrated layer can enhance the corrosive-wear resistance of the Ti6Al4V titanium alloy
To improve the corrosive-wear resistance of the Ti6Al4V titanium alloy, W-Mo co-penetrated layer was prepared on Ti6Al4V titanium alloy surface by double glow discharge technique. The corrosive-wear properties of the co-penetrated layer were investigated. The results show that W-Mo co-penetrated layer combined well with the substrate, and the layer was composed of deposited layer, transition layer and diffused layer. Compared with Ti6Al4V substrate, the alloying layer exhibited a lower friction coefficient, improved wear morphology and an obviously decreased wearing volume in 5wt%NaCl and 5wt% H2SO4 solutions. All these indicate that W-Mo co-penetrated layer can enhance the corrosive-wear resistance of the Ti6Al4V titanium alloy
2013, 42(1):211-214.
Abstract:
In order to improve the electrocatalytic activity of Pt based catalyst to small organic molecules oxidation, the SiW12 modified Pt electrodes were prepared, and its electrocatalytic activities for the small organic molecules oxidation were evaluated by cyclic voltammetry scanning. The results show that the electrocatalytic activity to small organic molecules oxidation of platinum electrode can be improved by modification of SiW12
In order to improve the electrocatalytic activity of Pt based catalyst to small organic molecules oxidation, the SiW12 modified Pt electrodes were prepared, and its electrocatalytic activities for the small organic molecules oxidation were evaluated by cyclic voltammetry scanning. The results show that the electrocatalytic activity to small organic molecules oxidation of platinum electrode can be improved by modification of SiW12
2013, 42(1):215-220.
Abstract:
对SiC纤维增强Ti基复合材料(SiCf/Ti)疲劳损伤机制、疲劳寿命及其影响因素进行详细的回顾，并重点综述了影响SiCf/Ti寿命的主要因素，包括外在因素(控制模式、应力比、加载频率、温度和环境)和内在因素(基体合金、纤维性质、纤维体积分数、界面和纤维涂层)，提出了当前研究存在的问题和今后潜在的发展方向
对SiC纤维增强Ti基复合材料(SiCf/Ti)疲劳损伤机制、疲劳寿命及其影响因素进行详细的回顾，并重点综述了影响SiCf/Ti寿命的主要因素，包括外在因素(控制模式、应力比、加载频率、温度和环境)和内在因素(基体合金、纤维性质、纤维体积分数、界面和纤维涂层)，提出了当前研究存在的问题和今后潜在的发展方向
