Volume 41,Issue 2,2012 Table of Contents
2012, 41(2):189-193.
Abstract:
The effects of Pr on the microstructure and magnetic properties of PrxCo50-xPt50 alloys (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were investigated. The XRD results indicate that all the alloys homogenized at 1000 °C contain only a single A1 (fcc) phase, while the alloys annealed at 675-750 °C consist of a hard-magnetic face-centered-tetragonal (fct) phase and a magnetically soft fcc phase. The (111) reflection belonging to the fct phase shifts to a higher angle and the c/a ratio increases as the Pr content increases, which leads to a decrease in the degree of ordering, S. Maximum values for the coercivity Hc and the remanence ratio mr are achieved in Pr0.4Co49.6Pt50 alloys annealed at 675 °C for 60 min. For the series of PrxCo50-xPt50 alloys annealed at 675 °C for 60 min, Hc decreases monotonically with increasing of Pr concentration, but mr is first enhanced and then weakened, showing a maximum value of 0.82 at x = 0.4 to 0.6.
The effects of Pr on the microstructure and magnetic properties of PrxCo50-xPt50 alloys (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were investigated. The XRD results indicate that all the alloys homogenized at 1000 °C contain only a single A1 (fcc) phase, while the alloys annealed at 675-750 °C consist of a hard-magnetic face-centered-tetragonal (fct) phase and a magnetically soft fcc phase. The (111) reflection belonging to the fct phase shifts to a higher angle and the c/a ratio increases as the Pr content increases, which leads to a decrease in the degree of ordering, S. Maximum values for the coercivity Hc and the remanence ratio mr are achieved in Pr0.4Co49.6Pt50 alloys annealed at 675 °C for 60 min. For the series of PrxCo50-xPt50 alloys annealed at 675 °C for 60 min, Hc decreases monotonically with increasing of Pr concentration, but mr is first enhanced and then weakened, showing a maximum value of 0.82 at x = 0.4 to 0.6.
2012, 41(2):194-198.
Abstract:
The microstructure, hardness and isothermal oxidation behavior of CoNiCrAlY alloy modified by addition of 3 wt% and 5 wt% Pt were investigated using scanning electron microscopy, Vickers hardness tester, X-ray diffraction and energy dispersive spectroscopy analysis. The results reveal that Pt has a significant influence on the microstructure of the experimental alloy by formation of β-(Ni,Pt)Al phase. Addition of Pt can slightly increase the hardness of the experimental alloys. Pt will accelerate the phase transformation of alumina from metastable θ-Al2O3 to stable α-Al2O3, which is the main reason for the lowering oxidation rate and the formation of a protective oxide scale on the Pt-containing alloys. Furthermore, adding of Pt can improve the Al transport, which suppresses the consumption of β-phase and eliminates the internal oxidation.
The microstructure, hardness and isothermal oxidation behavior of CoNiCrAlY alloy modified by addition of 3 wt% and 5 wt% Pt were investigated using scanning electron microscopy, Vickers hardness tester, X-ray diffraction and energy dispersive spectroscopy analysis. The results reveal that Pt has a significant influence on the microstructure of the experimental alloy by formation of β-(Ni,Pt)Al phase. Addition of Pt can slightly increase the hardness of the experimental alloys. Pt will accelerate the phase transformation of alumina from metastable θ-Al2O3 to stable α-Al2O3, which is the main reason for the lowering oxidation rate and the formation of a protective oxide scale on the Pt-containing alloys. Furthermore, adding of Pt can improve the Al transport, which suppresses the consumption of β-phase and eliminates the internal oxidation.
2012, 41(2):199-202.
Abstract:
The effects of the processing parameters on the deformation behavior of Ti14 alloy containing a small volume of liquid have been investigated through compressive tests. Experiments were conducted at deformation temperatures from 1000 to 1150 °C, strain rates from 5×10-3 to 5 s-1 and deformation degrees from 40% to 70%. The results show that deformation temperature and strain rate have significant effects on the peak flow stress. The flow stress decreases with increasing of deformation temperature and/or decreasing of strain rate. The response time required by deformation is affected by the strain rate and liquid fraction is controlled by the temperature. As the temperature increases, deformation mechanism transforms from sliding between solid particles (SS) to the flow of liquid incorporating solid particles (FLS), which improves the semi-solid deformation behavior. In addition, the flow stress decreases with increasing of deformation degrees during the compression which is associated with lubricating effect of liquid during semi-solid deformation.
The effects of the processing parameters on the deformation behavior of Ti14 alloy containing a small volume of liquid have been investigated through compressive tests. Experiments were conducted at deformation temperatures from 1000 to 1150 °C, strain rates from 5×10-3 to 5 s-1 and deformation degrees from 40% to 70%. The results show that deformation temperature and strain rate have significant effects on the peak flow stress. The flow stress decreases with increasing of deformation temperature and/or decreasing of strain rate. The response time required by deformation is affected by the strain rate and liquid fraction is controlled by the temperature. As the temperature increases, deformation mechanism transforms from sliding between solid particles (SS) to the flow of liquid incorporating solid particles (FLS), which improves the semi-solid deformation behavior. In addition, the flow stress decreases with increasing of deformation degrees during the compression which is associated with lubricating effect of liquid during semi-solid deformation.
2012, 41(2):203-207.
Abstract:
Intermetallics of Fe40Al, Ni3Al and TiAl(NbCr) were used as matrix to effectively bond a layer of TiC sintered body with low porosity. The coupled intermetallic and the TiC sintered body were held at high temperatures and a given pressure. The microstructure of the interface was observed and analyzed by scanning electron microscopy (SEM) and energy dispersive spectra (EDS). The results show that the bond between the intermetallics and the TiC sintered body is a metallurgical bond. TiC slightly decomposes and diffuses into the surface layers of Fe40Al and Ni3Al during the holding time, resulting in decrease of their melting points, and hence the intermetallic is in a flowing state and intruded into the pores of the TiC sintered body at the interface. However, the TiAl(NbCr) alloy can not be intruded into the pores of TiC sintered body; instead, a distinct reaction layer with more than 10 at% Ti (higher compared with the matrix) is formed at the interface of the TiAl(NbCr) alloy and the TiC sintered body.
Intermetallics of Fe40Al, Ni3Al and TiAl(NbCr) were used as matrix to effectively bond a layer of TiC sintered body with low porosity. The coupled intermetallic and the TiC sintered body were held at high temperatures and a given pressure. The microstructure of the interface was observed and analyzed by scanning electron microscopy (SEM) and energy dispersive spectra (EDS). The results show that the bond between the intermetallics and the TiC sintered body is a metallurgical bond. TiC slightly decomposes and diffuses into the surface layers of Fe40Al and Ni3Al during the holding time, resulting in decrease of their melting points, and hence the intermetallic is in a flowing state and intruded into the pores of the TiC sintered body at the interface. However, the TiAl(NbCr) alloy can not be intruded into the pores of TiC sintered body; instead, a distinct reaction layer with more than 10 at% Ti (higher compared with the matrix) is formed at the interface of the TiAl(NbCr) alloy and the TiC sintered body.
2012, 41(2):208-211.
Abstract:
For the orthogonal TA2M sheet metal, a usable triangle function used to describe the variation of anisotropy R is presented. Based on above description of value R, a new hypothesis that the potential values on flange outer boundary is regularly arranged according to the distribution law of anisotropy R has been proposed and the potential theory and boundary element method are used to calculate the reasonable blank shape which will provide a good method to control the deep-drawing ear for the orthotropic TA2M sheet metal. Through practical application, the presented blank design approach is approved to be efficient for the control of deep-drawing ear.
For the orthogonal TA2M sheet metal, a usable triangle function used to describe the variation of anisotropy R is presented. Based on above description of value R, a new hypothesis that the potential values on flange outer boundary is regularly arranged according to the distribution law of anisotropy R has been proposed and the potential theory and boundary element method are used to calculate the reasonable blank shape which will provide a good method to control the deep-drawing ear for the orthotropic TA2M sheet metal. Through practical application, the presented blank design approach is approved to be efficient for the control of deep-drawing ear.
2012, 41(2):212-214.
Abstract:
Effects of Ti and C addition on crystallization process and magnetic properties of NdPrFeB thick ribbons were investigated. The results show that doping of Ti suppresses the formation of (Nd,Pr)2Fe23B3 metastable phase and refines grains of the alloys and increases coercivity significantly. In the case of co-addition of Ti and C, the coercivity is decreased but the remanence is enhanced with increasing of C content. The magnetic properties of Jr=0.88 T, Hcj=618 kA/m and (BH)max=109.8 kJ/m3 are achieved in the (Nd0.4Pr0.6)9Fe72Ti4B11C4 ribbons after optimal annealing.
Effects of Ti and C addition on crystallization process and magnetic properties of NdPrFeB thick ribbons were investigated. The results show that doping of Ti suppresses the formation of (Nd,Pr)2Fe23B3 metastable phase and refines grains of the alloys and increases coercivity significantly. In the case of co-addition of Ti and C, the coercivity is decreased but the remanence is enhanced with increasing of C content. The magnetic properties of Jr=0.88 T, Hcj=618 kA/m and (BH)max=109.8 kJ/m3 are achieved in the (Nd0.4Pr0.6)9Fe72Ti4B11C4 ribbons after optimal annealing.
2012, 41(2):215-220.
Abstract:
Equal-channel angular pressing (ECAP) was conducted on Mg-1.5Mn-0.3Ce magnesium alloy at 623 K using route Bc to investigate its microstructure, the texture and mechanical properties. The microstructure observation indicates that grains are obviously refined by ECAP, the smallest grain size of ECAPed magnesium alloy is about 1.2 μm after sixth pass ECAP from 26.1 μm of as-rolled one, and numbers of tiny Mg12Ce dispersively distribute in intragranular and intergranular regions. At the same time, the texture of as-rolled magnesium alloy is reduced gradually and starts to change to ECAPed texture when the texture intensity rises with the increase of ECAP passes. Mechanical properties show that the tensile strength and yield strength are raised with ECAP passes before three passes, matching the relationship of Hall-Petch because grain refinement is more significant than texture softening, and gets the maximum values of 272.2 MPa and 263.7 MPa at the third pass deformation. When the passes continue to increase to four passes, the strength is declined in contradiction to Hall-Petch relationship due to formed non-basic texture. The tensile-to-failure morphologies reveal that fractured mode is along the grain boundary for as-rolled and ECAPed magnesium alloys, and there are more dimples for sixth pass with the biggest elongation of 16.8 % at room temperature.
Equal-channel angular pressing (ECAP) was conducted on Mg-1.5Mn-0.3Ce magnesium alloy at 623 K using route Bc to investigate its microstructure, the texture and mechanical properties. The microstructure observation indicates that grains are obviously refined by ECAP, the smallest grain size of ECAPed magnesium alloy is about 1.2 μm after sixth pass ECAP from 26.1 μm of as-rolled one, and numbers of tiny Mg12Ce dispersively distribute in intragranular and intergranular regions. At the same time, the texture of as-rolled magnesium alloy is reduced gradually and starts to change to ECAPed texture when the texture intensity rises with the increase of ECAP passes. Mechanical properties show that the tensile strength and yield strength are raised with ECAP passes before three passes, matching the relationship of Hall-Petch because grain refinement is more significant than texture softening, and gets the maximum values of 272.2 MPa and 263.7 MPa at the third pass deformation. When the passes continue to increase to four passes, the strength is declined in contradiction to Hall-Petch relationship due to formed non-basic texture. The tensile-to-failure morphologies reveal that fractured mode is along the grain boundary for as-rolled and ECAPed magnesium alloys, and there are more dimples for sixth pass with the biggest elongation of 16.8 % at room temperature.
2012, 41(2):221-225.
Abstract:
The microtexture of AZ31 magnesium alloy with compression deformation was studied by electron backscatter diffraction (EBSD) in situ tracking. The microtexture evolvement of the same observation areas of the alloy sheets which were compressed three times continually (deformation of 11%, 17% and 23%, respectively) were investigated. The results show that the microtexture of as-rolled AZ31 magnesium alloy is typical (0001) basic texture. With deformation of 11% and the temperature of 170 oC, the grain orientation changes remarkably, most grains have been twined fully and a few grains twined partially. The initial basic rolled texture is weakened a lot, and twined grains tropism accord with 60°/ and 86.3°/ orientation. With the increasing of deformation, sliding is start-up, twined boundary decreases and variation of microtexture is not obvious. In compression deformation of AZ31 magnesium alloy, the evolution mechanism of microtexture is the tension twinning, without compression twinning.
The microtexture of AZ31 magnesium alloy with compression deformation was studied by electron backscatter diffraction (EBSD) in situ tracking. The microtexture evolvement of the same observation areas of the alloy sheets which were compressed three times continually (deformation of 11%, 17% and 23%, respectively) were investigated. The results show that the microtexture of as-rolled AZ31 magnesium alloy is typical (0001) basic texture. With deformation of 11% and the temperature of 170 oC, the grain orientation changes remarkably, most grains have been twined fully and a few grains twined partially. The initial basic rolled texture is weakened a lot, and twined grains tropism accord with 60°/ and 86.3°/ orientation. With the increasing of deformation, sliding is start-up, twined boundary decreases and variation of microtexture is not obvious. In compression deformation of AZ31 magnesium alloy, the evolution mechanism of microtexture is the tension twinning, without compression twinning.
2012, 41(2):226-229.
Abstract:
The evolution of microstructure and texture after final annealing treatment of two kinds of zirconium-based alloys with different composition (Zr-Nb, Zr-Sn-Nb) was investigated by electron backscatter diffraction (EBSD). The misorientation of the recrystallized grains was characterized. The results show that the grains of the alloys after final annealing treatment are uniform and equiaxed, and most of the grain sizes range from 2 to 5 μm; the second phase particles (SPPs) are very different for the two kinds of alloys. The SPPs disperse evenly in Zr-Sn-Nb, while in the Zr-Nb, there are two kinds of SPPs. The main texture of the alloys after final annealing is the basal texture, and the maximum is spread out towards the transverse direction. And the < > directions are parallel to the rolling direction.
The evolution of microstructure and texture after final annealing treatment of two kinds of zirconium-based alloys with different composition (Zr-Nb, Zr-Sn-Nb) was investigated by electron backscatter diffraction (EBSD). The misorientation of the recrystallized grains was characterized. The results show that the grains of the alloys after final annealing treatment are uniform and equiaxed, and most of the grain sizes range from 2 to 5 μm; the second phase particles (SPPs) are very different for the two kinds of alloys. The SPPs disperse evenly in Zr-Sn-Nb, while in the Zr-Nb, there are two kinds of SPPs. The main texture of the alloys after final annealing is the basal texture, and the maximum is spread out towards the transverse direction. And the < > directions are parallel to the rolling direction.
2012, 41(2):230-234.
Abstract:
The effect of long-term aging on microstructure and creep properties of a single crystal Ni-based superalloy was investigated. The results show that the g ￠ phase remains cubic distribution after aging at 800 oC for 1000 h; the g ￠ phase gradually connects and rafts after aging at 980 oC for 1000 h or at 1010 oC for 500 h. The μ phase precipitates in the form of needles and granules when aged at 980 oC for more than 500 h or at 1010 oC for more than 100 h; the μ phase gradually increases with the aging time prolonging at 980 oC, while it first increases and then decreases when aged at 1010 oC. The creep lives of the alloy change a little after long-term aging at 800 oC, while the lives decrease with increasing of aging time and temperatures at 980 and 1010 oC.
The effect of long-term aging on microstructure and creep properties of a single crystal Ni-based superalloy was investigated. The results show that the g ￠ phase remains cubic distribution after aging at 800 oC for 1000 h; the g ￠ phase gradually connects and rafts after aging at 980 oC for 1000 h or at 1010 oC for 500 h. The μ phase precipitates in the form of needles and granules when aged at 980 oC for more than 500 h or at 1010 oC for more than 100 h; the μ phase gradually increases with the aging time prolonging at 980 oC, while it first increases and then decreases when aged at 1010 oC. The creep lives of the alloy change a little after long-term aging at 800 oC, while the lives decrease with increasing of aging time and temperatures at 980 and 1010 oC.
2012, 41(2):241-245.
Abstract:
The creep behavior of Pt-5Ir and ZGSPt-5Ir high-temperature materials in the temperature range of 1423-1523 K were investigated. The results show that the creep property of ZGSPt-5Ir is better than that of Pt-5Ir because of ZrO2 addition. The creep characteristic of ZGSPt-5Ir is consistent with a structure-controlled creep process where some form of dislocation climb caused by lattice self-diffusion controls the creep deformation. And the fracture mode is brittle intergranular fracture. The creep characteristic of Pt-5Ir is consistent with mobility-controlled deformation where viscous glide of dislocations controls the creep. And the fracture mode of that is transgranular ductile fracture.
The creep behavior of Pt-5Ir and ZGSPt-5Ir high-temperature materials in the temperature range of 1423-1523 K were investigated. The results show that the creep property of ZGSPt-5Ir is better than that of Pt-5Ir because of ZrO2 addition. The creep characteristic of ZGSPt-5Ir is consistent with a structure-controlled creep process where some form of dislocation climb caused by lattice self-diffusion controls the creep deformation. And the fracture mode is brittle intergranular fracture. The creep characteristic of Pt-5Ir is consistent with mobility-controlled deformation where viscous glide of dislocations controls the creep. And the fracture mode of that is transgranular ductile fracture.
2012, 41(2):246-250.
Abstract:
Based on the microscopic phase-field kinetic model and the microelasticity theory, the precipitation process and the atomic site occupation of γ′ phase of Ni75Al15Mn10 alloy were simulated. The results indicate that when the alloy is aged at 1273 K, L10 phase is formed firstly, and then gradually transformed into L12 phase with the development of the long range order parameter at the initial precipitation stage. Atomic ordering precedes compositional clustering, and γ′ phase precipitation is of the congruent ordering + spinodal mechanism. The volume of γ′ ordered phase is less than that of γ phase, and the volume ratio of the ordered to the disordered is about 60%. The β site is mostly occupied by Al atoms (the corner site of γ′ phase), while the αⅡ and αⅠ sites are mostly occupied by Mn atoms; moreover, the occupation probability at αⅡ site is higher than that of αⅠ site, Mn atoms mostly occupies the site of Ni atoms, and the precipitated γ′ phase is a kind of (Ni, Mn)3Al phase.
Based on the microscopic phase-field kinetic model and the microelasticity theory, the precipitation process and the atomic site occupation of γ′ phase of Ni75Al15Mn10 alloy were simulated. The results indicate that when the alloy is aged at 1273 K, L10 phase is formed firstly, and then gradually transformed into L12 phase with the development of the long range order parameter at the initial precipitation stage. Atomic ordering precedes compositional clustering, and γ′ phase precipitation is of the congruent ordering + spinodal mechanism. The volume of γ′ ordered phase is less than that of γ phase, and the volume ratio of the ordered to the disordered is about 60%. The β site is mostly occupied by Al atoms (the corner site of γ′ phase), while the αⅡ and αⅠ sites are mostly occupied by Mn atoms; moreover, the occupation probability at αⅡ site is higher than that of αⅠ site, Mn atoms mostly occupies the site of Ni atoms, and the precipitated γ′ phase is a kind of (Ni, Mn)3Al phase.
2012, 41(2):251-255.
Abstract:
The hot deformation behavior of as-cast TC21 alloy was investigated in the temperature range of 1000-1150 oC and the strain rate range of 0.01-10 s-1. Based on dynamic materials modeling (DMM), the processing map was established. Combined with the microstructure observation the hot deformation mechanism of TC21 alloy was worked out. The results show that the leading deformation mechanism of TC21 alloy is dynamic recovery in β region. At higher strain rate ( ≥1 s-1), the instability is attributed to flow localization, which should be avoided. The second domain (1050-1120 oC, 0.1-1 s-1), β grain boundary represents sliding, which is typical dynamic recovery. Optimal processing zone appears at the lower strain rate (0.01-0.1 s-1), which has a peak efficiency of 38%-46%, and a typical continuous recrystallization with serrated grain boundaries occurs. Thus, the first cogging should be at a higher temperature (1150 oC) to avoid cracking. Later, it should be at a lower temperature to obtain fine and homogeneous microstructure.
The hot deformation behavior of as-cast TC21 alloy was investigated in the temperature range of 1000-1150 oC and the strain rate range of 0.01-10 s-1. Based on dynamic materials modeling (DMM), the processing map was established. Combined with the microstructure observation the hot deformation mechanism of TC21 alloy was worked out. The results show that the leading deformation mechanism of TC21 alloy is dynamic recovery in β region. At higher strain rate ( ≥1 s-1), the instability is attributed to flow localization, which should be avoided. The second domain (1050-1120 oC, 0.1-1 s-1), β grain boundary represents sliding, which is typical dynamic recovery. Optimal processing zone appears at the lower strain rate (0.01-0.1 s-1), which has a peak efficiency of 38%-46%, and a typical continuous recrystallization with serrated grain boundaries occurs. Thus, the first cogging should be at a higher temperature (1150 oC) to avoid cracking. Later, it should be at a lower temperature to obtain fine and homogeneous microstructure.
2012, 41(2):256-259.
Abstract:
Nanocrystalline (W, Ni, Fe, La) composite powders were prepared by a multi-step process, consisting of sol-spray drying, calcination and subsequent hydrogen reduction process. The mechanism of the influence of La on grain growth and bubbling inhabitation during the liquid-phase sintering of the nanocrystalline (W, Ni, Fe, La) composite powders were studied. The phase transformation involved with La during the sintering of the composite powders was investigated. The distribution and existing form of La in the alloy were studied. The results show that the La2WO6 and La4W2O15 are formed in the synthesized nanocrystalline powders. In the sintered alloy, the rare-earth La is dispersed in the γ-(Ni, Fe) phase and converts into the La4W2O15 phase which can be stable at a high temperature. The La4W2O15 phase has a strong affinity with the impurities of Ca and O elements, playing the roles in purifying the grain boundaries and intracrystalline. The diffusion of W into the γ-(Ni, Fe) phase during liquid-phase sintering is inhibited and thus the solution of W in γ-(Ni, Fe) phase is significantly reduced by the second-phase particles, which slows down the solution-precipitation process and inhibits the grain growth as well as bubbling during liquid-phase sintering process.
Nanocrystalline (W, Ni, Fe, La) composite powders were prepared by a multi-step process, consisting of sol-spray drying, calcination and subsequent hydrogen reduction process. The mechanism of the influence of La on grain growth and bubbling inhabitation during the liquid-phase sintering of the nanocrystalline (W, Ni, Fe, La) composite powders were studied. The phase transformation involved with La during the sintering of the composite powders was investigated. The distribution and existing form of La in the alloy were studied. The results show that the La2WO6 and La4W2O15 are formed in the synthesized nanocrystalline powders. In the sintered alloy, the rare-earth La is dispersed in the γ-(Ni, Fe) phase and converts into the La4W2O15 phase which can be stable at a high temperature. The La4W2O15 phase has a strong affinity with the impurities of Ca and O elements, playing the roles in purifying the grain boundaries and intracrystalline. The diffusion of W into the γ-(Ni, Fe) phase during liquid-phase sintering is inhibited and thus the solution of W in γ-(Ni, Fe) phase is significantly reduced by the second-phase particles, which slows down the solution-precipitation process and inhibits the grain growth as well as bubbling during liquid-phase sintering process.
2012, 41(2):260-265.
Abstract:
The critical plastic shear strain corresponding to the onset of adiabatic shear band for Ti-6Al-4V alloy is calculated based on the curve-fitting least-squares method. Using gradient-dependent plasticity, the local plastic shear deformation distribution in the adiabatic shear band is obtained theoretically to fit the experimental flow lines by Liao and Duffy (1998). The critical plastic shear strains at different values of the adiabatic shear band width are assessed. When the width is assigned to be in the range of 1-2 mm, the predicted critical plastic shear strain is in the range of 0.1-0.47. It is found that the theoretical expression for the local plastic shear deformation distribution in the adiabatic shear band can well describe the nonlinear characteristics of flow lines. When the width is assigned to be a higher value, the theoretical flow lines in the adiabatic shear band are more curved at the two ends of the band, while when the width is assigned to be a lower value, the theoretical flow lines are straighter and only slightly curved.
The critical plastic shear strain corresponding to the onset of adiabatic shear band for Ti-6Al-4V alloy is calculated based on the curve-fitting least-squares method. Using gradient-dependent plasticity, the local plastic shear deformation distribution in the adiabatic shear band is obtained theoretically to fit the experimental flow lines by Liao and Duffy (1998). The critical plastic shear strains at different values of the adiabatic shear band width are assessed. When the width is assigned to be in the range of 1-2 mm, the predicted critical plastic shear strain is in the range of 0.1-0.47. It is found that the theoretical expression for the local plastic shear deformation distribution in the adiabatic shear band can well describe the nonlinear characteristics of flow lines. When the width is assigned to be a higher value, the theoretical flow lines in the adiabatic shear band are more curved at the two ends of the band, while when the width is assigned to be a lower value, the theoretical flow lines are straighter and only slightly curved.
2012, 41(2):266-270.
Abstract:
Fracture and block flaking off caused by surface micro-cracks are the main failure mode of CuW contact. Finite element method was applied to analyze temperature and stress distribution of CuW contact by thermo-elastic effect under arc thermal load considering the arc heat distribution in time and space, temperature dependent material properties and latent heat at high temperature. According to the thermal stress distribution, cracks nucleation process and places were predicated under driving force on component, thus providing foundation for the damage analysis of contact.
Fracture and block flaking off caused by surface micro-cracks are the main failure mode of CuW contact. Finite element method was applied to analyze temperature and stress distribution of CuW contact by thermo-elastic effect under arc thermal load considering the arc heat distribution in time and space, temperature dependent material properties and latent heat at high temperature. According to the thermal stress distribution, cracks nucleation process and places were predicated under driving force on component, thus providing foundation for the damage analysis of contact.
2012, 41(2):271-275.
Abstract:
The structures, electronic properties, elasticity, theoretic hardness, and Debye temperatures of chromium carbides, Cr3C2, Cr7C3 and Cr23C6 were calculated by the density functional theory of first-principles. The results show that the deviation of equilibrium lattice parameters from the experimental data is small. The bond in these compounds is the mixture of covalent, ionic and metallic bonding. The most stable phase belongs to Cr3C2; the values of theoretic hardness of Cr3C2, Cr7C3 and Cr23C6 are 20.9, 18.3 and 13.2 GPa, respectively, which are in good agreement with recent experimental results. Besides, the Debye temperatures of chromium carbides were predicted.
The structures, electronic properties, elasticity, theoretic hardness, and Debye temperatures of chromium carbides, Cr3C2, Cr7C3 and Cr23C6 were calculated by the density functional theory of first-principles. The results show that the deviation of equilibrium lattice parameters from the experimental data is small. The bond in these compounds is the mixture of covalent, ionic and metallic bonding. The most stable phase belongs to Cr3C2; the values of theoretic hardness of Cr3C2, Cr7C3 and Cr23C6 are 20.9, 18.3 and 13.2 GPa, respectively, which are in good agreement with recent experimental results. Besides, the Debye temperatures of chromium carbides were predicted.
2012, 41(2):281-284.
Abstract:
The formation process and growth kinetics of the intermetallic (IMC) layers at the solid-state diffusion-bonded interface between the Cu and Al foils conducted by plasma activated sintering processing were investigated in the temperature range of 673-773 K. The results show that the formation process of the IMCs involves four stages, physical contact, IMCs nucleation, IMCs connection along the interface and continuous thickening of the IMC layers. The interfacial region is composed of Al4Cu9, AlCu and Al2Cu layers. The relationships between each layer thickness and the reaction time follow the approximate parabolic law, indicating the diffusion-controlled growth kinetic of the IMCs. The growth rate constants of the IMC layers conform to the Arrhenius relation with temperature, and the calculated activation energies for the growth of total IMCs, Al4Cu9, AlCu and Al2Cu layers are 80.78, 89.79, 84.63 and 71.12 kJ/mol, respectively.
The formation process and growth kinetics of the intermetallic (IMC) layers at the solid-state diffusion-bonded interface between the Cu and Al foils conducted by plasma activated sintering processing were investigated in the temperature range of 673-773 K. The results show that the formation process of the IMCs involves four stages, physical contact, IMCs nucleation, IMCs connection along the interface and continuous thickening of the IMC layers. The interfacial region is composed of Al4Cu9, AlCu and Al2Cu layers. The relationships between each layer thickness and the reaction time follow the approximate parabolic law, indicating the diffusion-controlled growth kinetic of the IMCs. The growth rate constants of the IMC layers conform to the Arrhenius relation with temperature, and the calculated activation energies for the growth of total IMCs, Al4Cu9, AlCu and Al2Cu layers are 80.78, 89.79, 84.63 and 71.12 kJ/mol, respectively.
2012, 41(2):285-288.
Abstract:
The degradation mechanism of Ti0.26Zr0.07V0.24Mn0.1Ni0.33 alloy electrode was investigated by means of FESEM-EDS, EIS and ICP-MS. The decrease of hydrogen diffusion coefficient (D), the increase of charge transfer resistances (Rct), and the dissolution of V, Ti and Zr elements to KOH solution with charge/discharge cycling should be responsible for the performances degradation of the alloy electrode.
The degradation mechanism of Ti0.26Zr0.07V0.24Mn0.1Ni0.33 alloy electrode was investigated by means of FESEM-EDS, EIS and ICP-MS. The decrease of hydrogen diffusion coefficient (D), the increase of charge transfer resistances (Rct), and the dissolution of V, Ti and Zr elements to KOH solution with charge/discharge cycling should be responsible for the performances degradation of the alloy electrode.
2012, 41(2):289-293.
Abstract:
By means of molecular dynamics (MD) simulations, the melting mechanism of thin W(111) and W(110) planes with free surfaces has been studied with the modified analytic embedded-atom method (MAEAM). Firstly, the results obtained by calculating the temperature dependence of mean square displacement (MSD) indicate that the influence of surface and anharmonic effect on the microstructure and properties of planes are significant and the vibration of atoms locating in the surface region is anisotropic. Then, according to providing further investigation into the temperature dependence of the atomic density function (ADF) and structural factor (SF) of the given atomic planes, it is found that the melting mechanisms and processes of both membranes are different. For the W(111) plane, the free surface plays an important role in the melting transition. The W(111) plane entirely becomes disordering at 3700 K which is in agreement with the calculated melting temperature. The fitted relation between the fraction of the disordered atom and the temperature demonstrates that the premelting-melting transition temperature is about 3550 K. Instead, the W(110) plane is melted when the temperature reaches 4000 K, which is so-called superheating. And the melting transition of this plane relies strongly on the anharmonic effect.
By means of molecular dynamics (MD) simulations, the melting mechanism of thin W(111) and W(110) planes with free surfaces has been studied with the modified analytic embedded-atom method (MAEAM). Firstly, the results obtained by calculating the temperature dependence of mean square displacement (MSD) indicate that the influence of surface and anharmonic effect on the microstructure and properties of planes are significant and the vibration of atoms locating in the surface region is anisotropic. Then, according to providing further investigation into the temperature dependence of the atomic density function (ADF) and structural factor (SF) of the given atomic planes, it is found that the melting mechanisms and processes of both membranes are different. For the W(111) plane, the free surface plays an important role in the melting transition. The W(111) plane entirely becomes disordering at 3700 K which is in agreement with the calculated melting temperature. The fitted relation between the fraction of the disordered atom and the temperature demonstrates that the premelting-melting transition temperature is about 3550 K. Instead, the W(110) plane is melted when the temperature reaches 4000 K, which is so-called superheating. And the melting transition of this plane relies strongly on the anharmonic effect.
2012, 41(2):294-297.
Abstract:
The relationships of the surface roughness, hardness and elastic modulus to the friction properties were studied based on objects of a medical NiTi wire, a medical stainless steel wire and four medical β-Ti wires. The results show that the most significant factor on the friction resistance is the surface roughness, and the friction resistance has a positive correlation with it. However, the friction resistance has a negative correlation with elastic modulus and hardness. By the regression fitting, the quantitative relationships between the surface roughness, elastic modulus, hardness and friction resistance is established, that is f = (E -0.02649)·(H-0.07035)·(Ra0.80625), R2 = 0.9982.
The relationships of the surface roughness, hardness and elastic modulus to the friction properties were studied based on objects of a medical NiTi wire, a medical stainless steel wire and four medical β-Ti wires. The results show that the most significant factor on the friction resistance is the surface roughness, and the friction resistance has a positive correlation with it. However, the friction resistance has a negative correlation with elastic modulus and hardness. By the regression fitting, the quantitative relationships between the surface roughness, elastic modulus, hardness and friction resistance is established, that is f = (E -0.02649)·(H-0.07035)·(Ra0.80625), R2 = 0.9982.
2012, 41(2):298-303.
Abstract:
To gain ceramic coatings with biomechanical properties and meet the demand of clinical medicine, a (ZrO2)/hydroxyapatite (HA) composite ceramic coating was prepared by micro-arc oxidation in electrolyte with Ti6Al4V as substrate. The composition and the morphology of the coating were characterized by EDS and SEM, respectively. The mathematical model of biomechanics properties for the porous coatings was established and modified. The biomechanical properties of the coating were investigated by the combination of theoretical calculation and experiments. Results show that the (ZrO2)/HA composite coating of medical titanium alloy has better biomechanical properties than the individual hydroxyapatite ceramic coating. It is concluded that the mechanical properties and porosity of the bioceramic coating are related to the new phases. The mechanical properties of the ceramic coating can be better researched by the combination of theoretical model and experiments, and the established mathematical model is reasonable with certain theoretical meaning.
To gain ceramic coatings with biomechanical properties and meet the demand of clinical medicine, a (ZrO2)/hydroxyapatite (HA) composite ceramic coating was prepared by micro-arc oxidation in electrolyte with Ti6Al4V as substrate. The composition and the morphology of the coating were characterized by EDS and SEM, respectively. The mathematical model of biomechanics properties for the porous coatings was established and modified. The biomechanical properties of the coating were investigated by the combination of theoretical calculation and experiments. Results show that the (ZrO2)/HA composite coating of medical titanium alloy has better biomechanical properties than the individual hydroxyapatite ceramic coating. It is concluded that the mechanical properties and porosity of the bioceramic coating are related to the new phases. The mechanical properties of the ceramic coating can be better researched by the combination of theoretical model and experiments, and the established mathematical model is reasonable with certain theoretical meaning.
2012, 41(2):304-309.
Abstract:
The influences of hydrogen charging on microstructure and fatigue lives of electron beam welded TA15 alloys were studied. The microstructure observation shows that hydrogen exists in the alloy in the form of solid solution, and no hydride is formed when the hydrogen content is less than 0.105% (mass fraction). Fatigue life tests show that with the hydrogen content increasing, the fatigue life in the welded joints drops. It is because trace hydrogen decreases the toughness of TA15 alloy and solid-solution hydrogen increases the fatigue crack growth rate. In addition, the hydrogen atoms accelerate the fatigue crack propagation by influencing the behavior of crack tips. The existence of the "colony structures" in the fracture morphology reveals that the martensite packets perform as a unit, and hydrogen has some effects on the martensite packet during the crack propagation.
The influences of hydrogen charging on microstructure and fatigue lives of electron beam welded TA15 alloys were studied. The microstructure observation shows that hydrogen exists in the alloy in the form of solid solution, and no hydride is formed when the hydrogen content is less than 0.105% (mass fraction). Fatigue life tests show that with the hydrogen content increasing, the fatigue life in the welded joints drops. It is because trace hydrogen decreases the toughness of TA15 alloy and solid-solution hydrogen increases the fatigue crack growth rate. In addition, the hydrogen atoms accelerate the fatigue crack propagation by influencing the behavior of crack tips. The existence of the "colony structures" in the fracture morphology reveals that the martensite packets perform as a unit, and hydrogen has some effects on the martensite packet during the crack propagation.
2012, 41(2):310-314.
Abstract:
The hot deformation behavior of the cast Ni-35Cr based GH4648 superalloy was studied though hot compressing testing on a Gleeble-1500 simulator. The results show that the onset temperature of the dynamic recrystallization (DRX) in the cast GH4648 alloy is 1050 oC. The DRX process is going more sufficient with higher temperature. Below 1050 oC, there is no DRX grain. The effect of homogenization heat treatment on the hot working ability of cast GH4648 alloy was studied. After homogeneous heat treatment at 1180 oC for 45 h, the DRX process is restrained and resistance of deformation is increased.
The hot deformation behavior of the cast Ni-35Cr based GH4648 superalloy was studied though hot compressing testing on a Gleeble-1500 simulator. The results show that the onset temperature of the dynamic recrystallization (DRX) in the cast GH4648 alloy is 1050 oC. The DRX process is going more sufficient with higher temperature. Below 1050 oC, there is no DRX grain. The effect of homogenization heat treatment on the hot working ability of cast GH4648 alloy was studied. After homogeneous heat treatment at 1180 oC for 45 h, the DRX process is restrained and resistance of deformation is increased.
2012, 41(2):315-319.
Abstract:
The microstructure and cracking behavior of K418 superalloy applied in turbine blade by laser forming repair were investigated. The results indicate that laser repair zone (LRZ) is mainly composed of γ-FeCr0.29Ni0.16C0.06 solid solution matrix, cubic γ′ phase, rod or skeleton shaped primary MC and interdendritic (γ+MC) eutectic. MC carbides of cast substrate zone (CSZ) are blocky TiC distributing in intragranular and intergranular fields, but MC carbides of LRZ are skeleton or rod shaped (NbTi)C. From CSZ, heat affected zone (HAZ) to LRZ, the morphology, size and quantity of γ′ phases are different. The cracks of LRZ are solidification cracks related to the liquid film, and they propagate along interdendritic regions. Better parameters of LFR are achieved, and the tendency to crack of K418 alloy repaired by LFR is reduced greatly.
The microstructure and cracking behavior of K418 superalloy applied in turbine blade by laser forming repair were investigated. The results indicate that laser repair zone (LRZ) is mainly composed of γ-FeCr0.29Ni0.16C0.06 solid solution matrix, cubic γ′ phase, rod or skeleton shaped primary MC and interdendritic (γ+MC) eutectic. MC carbides of cast substrate zone (CSZ) are blocky TiC distributing in intragranular and intergranular fields, but MC carbides of LRZ are skeleton or rod shaped (NbTi)C. From CSZ, heat affected zone (HAZ) to LRZ, the morphology, size and quantity of γ′ phases are different. The cracks of LRZ are solidification cracks related to the liquid film, and they propagate along interdendritic regions. Better parameters of LFR are achieved, and the tendency to crack of K418 alloy repaired by LFR is reduced greatly.
2012, 41(2):320-323.
Abstract:
TiO2 films deposited on nano-grained titanium (NG Ti) and coarse-grained commercial pure titanium (CG Ti) by DC reactive magnetron sputtering were researched. The effects of NG Ti on the nucleation, growth, crystal structure and mechanical properties of the films were systematically studied. Scanning electron microscopy, atomic force microscope and X-ray diffraction were employed to characterize the surface morphology and crystal structure of TiO2 films. And scratch test, wear test and nanoindentation test were employed to characterize the interface bonding force, tribological properties and nanohardness of the films. The results show that NG Ti can greatly improve the nucleation rate and refine the grain size of the films, increase the nanohardness, the interface bonding force and the tribological properties of TiO2 films and promote the crystallization of rutile.
TiO2 films deposited on nano-grained titanium (NG Ti) and coarse-grained commercial pure titanium (CG Ti) by DC reactive magnetron sputtering were researched. The effects of NG Ti on the nucleation, growth, crystal structure and mechanical properties of the films were systematically studied. Scanning electron microscopy, atomic force microscope and X-ray diffraction were employed to characterize the surface morphology and crystal structure of TiO2 films. And scratch test, wear test and nanoindentation test were employed to characterize the interface bonding force, tribological properties and nanohardness of the films. The results show that NG Ti can greatly improve the nucleation rate and refine the grain size of the films, increase the nanohardness, the interface bonding force and the tribological properties of TiO2 films and promote the crystallization of rutile.
2012, 41(2):324-329.
Abstract:
A knitted gridding vertebral dilator of Ni-Ti shape memory alloy was designed to be used in the treatment of osteoporosis vertebral compressed fracture. The knitted gridding vertebral dilators with different parameters were knitted and their radial force and elastic modulus were tested; then the best knitted parameters were obtained. Taking into account of the practical application of the vertebral dilators, the structure of both ends of the dilator was improved and an innovative vertebral dilator was obtained which can meet the clinical application needs.
A knitted gridding vertebral dilator of Ni-Ti shape memory alloy was designed to be used in the treatment of osteoporosis vertebral compressed fracture. The knitted gridding vertebral dilators with different parameters were knitted and their radial force and elastic modulus were tested; then the best knitted parameters were obtained. Taking into account of the practical application of the vertebral dilators, the structure of both ends of the dilator was improved and an innovative vertebral dilator was obtained which can meet the clinical application needs.
2012, 41(2):330-334.
Abstract:
A low-cost vehicle titanium alloy (Ti-4.3Fe-7.1Cr-3Al) was prepared by spark plasma sintering process. Effects of the sintering temperature on the grain size, porosity, microstructure, composition uniformity, phase structure and mechanical properties were investigated. The results show that the microstructure of both samples sintered at 1100 or 1300 oC contain acicular α phase and β basic phase, with short strips and granular TiC distributing among them. Grain size and TiC precipitation density increase but the porosity and α phase decrease with the sintering temperature increasing, and the α phase distribution turns more and more even. Electron probe microanalysis shows that, the components have poor homogeneousness, segregation of Cr and Al occurs at 1100 oC, but disappears at 1300 oC. XRD analysis and nano-mechanical microprobe measurement show that additive elements cause the decrease of β phase lattice parameters and the precipitation of fine second phase, so the elastic modulus increases.
A low-cost vehicle titanium alloy (Ti-4.3Fe-7.1Cr-3Al) was prepared by spark plasma sintering process. Effects of the sintering temperature on the grain size, porosity, microstructure, composition uniformity, phase structure and mechanical properties were investigated. The results show that the microstructure of both samples sintered at 1100 or 1300 oC contain acicular α phase and β basic phase, with short strips and granular TiC distributing among them. Grain size and TiC precipitation density increase but the porosity and α phase decrease with the sintering temperature increasing, and the α phase distribution turns more and more even. Electron probe microanalysis shows that, the components have poor homogeneousness, segregation of Cr and Al occurs at 1100 oC, but disappears at 1300 oC. XRD analysis and nano-mechanical microprobe measurement show that additive elements cause the decrease of β phase lattice parameters and the precipitation of fine second phase, so the elastic modulus increases.
2012, 41(2):335-338.
Abstract:
The wettability and the interfacial interaction between pure liquid titanium and ZrO2 (CaO stabilized) were studied by the self-designed measuring apparatus in argon atmosphere. The morphology and element distribution of the liquid/solid cross section perpendicular to the interface were analyzed by SEM and EPMA. Results show that some chemical reaction occurs in the interface between pure liquid titanium and ZrO2 (CaO stabilized), but it is not severe. The molten titanium is not wet on the ZrO2 (CaO stabilized), with the contact angle of 103°. The total free energy variation of the Ti/zirconia system caused by the liquid/solid interface reaction can explain the influence of interfacial reaction on the wettability.
The wettability and the interfacial interaction between pure liquid titanium and ZrO2 (CaO stabilized) were studied by the self-designed measuring apparatus in argon atmosphere. The morphology and element distribution of the liquid/solid cross section perpendicular to the interface were analyzed by SEM and EPMA. Results show that some chemical reaction occurs in the interface between pure liquid titanium and ZrO2 (CaO stabilized), but it is not severe. The molten titanium is not wet on the ZrO2 (CaO stabilized), with the contact angle of 103°. The total free energy variation of the Ti/zirconia system caused by the liquid/solid interface reaction can explain the influence of interfacial reaction on the wettability.
2012, 41(2):339-342.
Abstract:
CoNiCu magnetic alloy nanowires were prepared in AAO templates by a pulse electrochemical deposition method. XRD measurements show that there are four magnetic phases in the nanowires, Co, Ni, NiCu and CoCu. The measured magnetic hysteresis loops taken along two directions (H is applied along or perpendicular to its longitudinal direction) show that the CoNiCu nanowire array has a weak anisotropy. The composites of magnetic alloy nanowires and wax have a good electromagnetic wave absorption property of GHz frequency. When the thickness of the absorbing coating is 4 mm, its minimum reflection loss can reach to –30 dB.
CoNiCu magnetic alloy nanowires were prepared in AAO templates by a pulse electrochemical deposition method. XRD measurements show that there are four magnetic phases in the nanowires, Co, Ni, NiCu and CoCu. The measured magnetic hysteresis loops taken along two directions (H is applied along or perpendicular to its longitudinal direction) show that the CoNiCu nanowire array has a weak anisotropy. The composites of magnetic alloy nanowires and wax have a good electromagnetic wave absorption property of GHz frequency. When the thickness of the absorbing coating is 4 mm, its minimum reflection loss can reach to –30 dB.
2012, 41(2):343-347.
Abstract:
Rhodium metal catalyst was used in the field of NBR homogeneous hydrogenation. A new extraction method of noble metal rhodium catalyst recovery from hydrogenated NBR (HNBR) solution has been researched. Rhodium metal catalyst can be efficiently removed from HNBR solution using SnCl2 as ligand and HCl as extractant. The condition of removing rhodium catalysts from HNBR solution has been studied, including reaction temperature, reaction time, SnCl2 concentration and proportion of aqueous phase to organic phase, and the removal of the rhodium metal catalyst is over 99% under the best conditions. IR and 1H NMR characterization show that HNBR structure and nitrile group have no change after rhodium metal catalyst is removed from HNBR solution.
Rhodium metal catalyst was used in the field of NBR homogeneous hydrogenation. A new extraction method of noble metal rhodium catalyst recovery from hydrogenated NBR (HNBR) solution has been researched. Rhodium metal catalyst can be efficiently removed from HNBR solution using SnCl2 as ligand and HCl as extractant. The condition of removing rhodium catalysts from HNBR solution has been studied, including reaction temperature, reaction time, SnCl2 concentration and proportion of aqueous phase to organic phase, and the removal of the rhodium metal catalyst is over 99% under the best conditions. IR and 1H NMR characterization show that HNBR structure and nitrile group have no change after rhodium metal catalyst is removed from HNBR solution.
2012, 41(2):348-351.
Abstract:
Well-dispersed Au colloids were prepared from AuCl3 and KBH4 under the protection of polyvinylpyrrolidone (PVP) in the ultrasonic field. The Au colloids were characterized by means of transmission electron microscope (TEM), X-ray diffraction (XRD) and spectrophotometer. The results indicate that Au nanoparticles are spherical or axiolitic and the grain diameter is about 25 nm. The reductant dosage has a great effect on the UV-vis absorption spectrum of Au colloids. When the dosage of KBH4 is lower than 1 mL, the maximum absorption peak is in 530 nm and the peak is low and broad. When the dosage of KBH4 is over 2 mL, the maximum absorption peak has a large blue shift to 512 -514 nm. The peak is strong and broad. When the dosage of KBH4 is over 5 mL, the absorbency graphs are alike. When the dosage of KBH4 is over 8 mL the maximum absorption peaks are in 510 nm around. The peak is strong, sharp and narrow, so the Au colloids are well-dispersed. The ultrasonic field distribution, power and temperature have a great effect on the absorbency graphs of Au colloids. The peaks are weak and the maximum peaks are in 510 nm around.
Well-dispersed Au colloids were prepared from AuCl3 and KBH4 under the protection of polyvinylpyrrolidone (PVP) in the ultrasonic field. The Au colloids were characterized by means of transmission electron microscope (TEM), X-ray diffraction (XRD) and spectrophotometer. The results indicate that Au nanoparticles are spherical or axiolitic and the grain diameter is about 25 nm. The reductant dosage has a great effect on the UV-vis absorption spectrum of Au colloids. When the dosage of KBH4 is lower than 1 mL, the maximum absorption peak is in 530 nm and the peak is low and broad. When the dosage of KBH4 is over 2 mL, the maximum absorption peak has a large blue shift to 512 -514 nm. The peak is strong and broad. When the dosage of KBH4 is over 5 mL, the absorbency graphs are alike. When the dosage of KBH4 is over 8 mL the maximum absorption peaks are in 510 nm around. The peak is strong, sharp and narrow, so the Au colloids are well-dispersed. The ultrasonic field distribution, power and temperature have a great effect on the absorbency graphs of Au colloids. The peaks are weak and the maximum peaks are in 510 nm around.
2012, 41(2):352-355.
Abstract:
Magnetic pulse welding between 1060 aluminum alloy and AZ31 magnesium alloy was conducted with different welding process parameters. Compared with the interface morphology of aluminum-aluminum joint, the characteristics of interface waves in Al-Mg dissimilar metal welding joint were discussed. With the help of SEM/EDS and the NANO INDENTER test analysis, the formation mechanism and the distribution of “melt zone”, and the change of hardness in this zone were investigated. The results show that the interface is of irregular wavy binding mode, and the interface wave embedded in the magnesium layer is much larger than that embedded in the aluminum wave; the “melt zone” will generate a rigid second phase, which is distributed in the Al-based side. Trough adjusting the appropriate welding parameters, it is obviously useful to avoid the formation of “melt zone”.
Magnetic pulse welding between 1060 aluminum alloy and AZ31 magnesium alloy was conducted with different welding process parameters. Compared with the interface morphology of aluminum-aluminum joint, the characteristics of interface waves in Al-Mg dissimilar metal welding joint were discussed. With the help of SEM/EDS and the NANO INDENTER test analysis, the formation mechanism and the distribution of “melt zone”, and the change of hardness in this zone were investigated. The results show that the interface is of irregular wavy binding mode, and the interface wave embedded in the magnesium layer is much larger than that embedded in the aluminum wave; the “melt zone” will generate a rigid second phase, which is distributed in the Al-based side. Trough adjusting the appropriate welding parameters, it is obviously useful to avoid the formation of “melt zone”.
2012, 41(2):356-359.
Abstract:
TiO2 nanotube arrays or nanoporous films fabricated by potentiostatic anodization of titanium (titanium alloy) in F--containing electrolytes constitute a material architecture that offers a large internal surface area and excellent electron percolation pathways for vectorial charge transfer between interfaces. The material architecture has proven to be of great interest for use in water photoelectrolysis, photocatalysis, heterojunction solar cells, and gas sensing. The parameters for TiO2 nanoporous film fabrication are found by changing the anodic oxidation voltage and phase composition of titanium alloys. When the anodization potential is below 30 V, TiO2 nanoporous film by anodizing TLM alloy aged at 550 oC for long time can be obtained.
TiO2 nanotube arrays or nanoporous films fabricated by potentiostatic anodization of titanium (titanium alloy) in F--containing electrolytes constitute a material architecture that offers a large internal surface area and excellent electron percolation pathways for vectorial charge transfer between interfaces. The material architecture has proven to be of great interest for use in water photoelectrolysis, photocatalysis, heterojunction solar cells, and gas sensing. The parameters for TiO2 nanoporous film fabrication are found by changing the anodic oxidation voltage and phase composition of titanium alloys. When the anodization potential is below 30 V, TiO2 nanoporous film by anodizing TLM alloy aged at 550 oC for long time can be obtained.
2012, 41(2):360-363.
Abstract:
Al coating on Mg alloy was prepared by plasma spraying technology, and it was then remelted by laser beam. The change of the coating before and after laser remelting was investigated using SEM, OM, XRD, tensile machine and salt spraying test. The results show that after laser remelting, the mechanical bond between the substrate and the coating changes to metallurgic bond and the adhesion strength is increased from 20.96 MPa to 22.13 MPa. The phase constituent keeps the same. Lots of pores occur in the coating and the porosity ratio is increased from 4.6% to 7.5%. The corrosion time is decreased from 900 h to 264 h.
Al coating on Mg alloy was prepared by plasma spraying technology, and it was then remelted by laser beam. The change of the coating before and after laser remelting was investigated using SEM, OM, XRD, tensile machine and salt spraying test. The results show that after laser remelting, the mechanical bond between the substrate and the coating changes to metallurgic bond and the adhesion strength is increased from 20.96 MPa to 22.13 MPa. The phase constituent keeps the same. Lots of pores occur in the coating and the porosity ratio is increased from 4.6% to 7.5%. The corrosion time is decreased from 900 h to 264 h.
2012, 41(2):364-367.
Abstract:
A kind of novel absorption material Nd4YFe88.5B6.5 was prepared by vacuum smelting, different ball milling time and proper annealing. The properties of the samples were tested. Results show that the microwave absorption values of all the unannealed and annealed samples are high and have a narrow range fluctuation. They increase with ball milling time prolonging and are improved greatly after annealing. The sample milled for 40 h owns the max absorption of 55.287 dB at the frequency of 10.63 GHz, while its absorption is improved greatly after annealing for 15 min at 550 oC, and the max absorption reaches to 132.415 dB at the frequency of 12.43 GHz. The causes of higher absorption properties were also discussed.
A kind of novel absorption material Nd4YFe88.5B6.5 was prepared by vacuum smelting, different ball milling time and proper annealing. The properties of the samples were tested. Results show that the microwave absorption values of all the unannealed and annealed samples are high and have a narrow range fluctuation. They increase with ball milling time prolonging and are improved greatly after annealing. The sample milled for 40 h owns the max absorption of 55.287 dB at the frequency of 10.63 GHz, while its absorption is improved greatly after annealing for 15 min at 550 oC, and the max absorption reaches to 132.415 dB at the frequency of 12.43 GHz. The causes of higher absorption properties were also discussed.
2012, 41(2):368-371.
Abstract:
Microstructure evolution principles of Ti-6Al-4V laser welding joints during superplastic deformation were analyzed, and some involved parameters were proposed to evaluate the forming process. The results indicate that during superplastic deformation the α′ martensite transformed into α+β phases, and needle-like structure transformed into lamellar structure. During superplastic deformation equiaxial rate increased with straining, and also increased with increasing forming temperature and decreasing strain rate. Average grain size was introduced to characterize the microstructure transition extent of HAZ, average grain size increasing with straining, and also increasing with increasing forming temperature and decreasing strain rate.
Microstructure evolution principles of Ti-6Al-4V laser welding joints during superplastic deformation were analyzed, and some involved parameters were proposed to evaluate the forming process. The results indicate that during superplastic deformation the α′ martensite transformed into α+β phases, and needle-like structure transformed into lamellar structure. During superplastic deformation equiaxial rate increased with straining, and also increased with increasing forming temperature and decreasing strain rate. Average grain size was introduced to characterize the microstructure transition extent of HAZ, average grain size increasing with straining, and also increasing with increasing forming temperature and decreasing strain rate.
2012, 41(2):372-376.
Abstract:
The aqueous rechargeable lithium ion battery hopefully becomes a new-type green power system because of its obvious advantages compared to the non-aqueous lithium ion cells, such as inherent safety, low cost, no environmental pollution, excellent production environment, promising high rate capability, relatively high energy and power densities. This paper summarizes several electrode systems of aqueous rechargeable lithium ion battery which are studied most recently at home and abroad. The current research situation of the relevant electrode materials and the fading mechanism of their performances have been reviewed. The trend of future research and the existing problems in the field of aqueous rechargeable lithium ion battery are also prospected.
The aqueous rechargeable lithium ion battery hopefully becomes a new-type green power system because of its obvious advantages compared to the non-aqueous lithium ion cells, such as inherent safety, low cost, no environmental pollution, excellent production environment, promising high rate capability, relatively high energy and power densities. This paper summarizes several electrode systems of aqueous rechargeable lithium ion battery which are studied most recently at home and abroad. The current research situation of the relevant electrode materials and the fading mechanism of their performances have been reviewed. The trend of future research and the existing problems in the field of aqueous rechargeable lithium ion battery are also prospected.
