The visco-plastic self-consistent (VPSC) model is extended to take the dynamical recrystallization (DRX) into account so that the hot extrusion texture of AZ80 magnesium alloy can be properly modeled. The effects of e...The visco-plastic self-consistent (VPSC) model is extended to take the dynamical recrystallization (DRX) into account so that the hot extrusion texture of AZ80 magnesium alloy can be properly modeled. The effects of extrusion temperatures and imposed boundary conditions on the resulting textures were investigated, and good agreement can be found between the simulated and the measured extrusion textures. The simulated results show that the DRX grains are responsible for the formation of the {2110} fiber component since the {1010} poles of the DRX grains are tilted away from those of the unrecrystallized grains during the formation of their high angle boundaries (HABs). Furthermore, the basal poles of the grains are favorably oriented to the transversal direction (TD) where the imposed deformation is larger due to lower slip resistance of the basal slip. The elevated temperature enhances the activity of pyramidal ?c+a? slip modes and gives rise to a larger recrystallized volume fraction, resulting in a weakened extrusion texture.展开更多
Three-dimensional（3D） geometric models with different comer angles （90° and 120°） and with or without inner round fillets in the bottom die were designed. Some important process parameters were regarded ...Three-dimensional（3D） geometric models with different comer angles （90° and 120°） and with or without inner round fillets in the bottom die were designed. Some important process parameters were regarded as the calculation conditions used in DEFORMTM-3D software, such as stress--strain data of compression test for AZ31 magnesium, temperatures of die and billet, and friction coefficient. Influence of friction coefficient on deformation process was discussed. The results show that reasonable lubrication condition is important to plastic deformation. The change characteristics for distributions of effective stress and strain during an equal channel angular extrusion （ECAE） process with inner angle of 90° and without fillets at outer comer were described. Inhomogeneity index （C） was defined and deformation heterogeneity of ECAE was analyzed from the simulation and experiment results. The deformation homogeneity caused by fillets at outer comer increased compared with the die without fillets. The cumulated maximum strains decrease with increasing the fillets of outer comer in ECAE die and the inner comer angle. The analysis results show that better structures of ECAE die including appropriate outer comer fillet and the inner comer angle of 90° for the die can improve the strain and ensure plastic deformation homogenization to a certain extent. The required extrusion force drops with increasing the fillet made at outer comer in ECAE die. It is demonstrated that the prediction results are in good agreement with experiments and the theoretical calculation and the research conclusions in literatures.展开更多
Semisolid billet of AZ80 magnesium alloy was prepared by new strain induced melt activated (new SIMA) process and thixoforging experiment was performed.The results show that after as-cast AZ80 magnesium alloy is proce...Semisolid billet of AZ80 magnesium alloy was prepared by new strain induced melt activated (new SIMA) process and thixoforging experiment was performed.The results show that after as-cast AZ80 magnesium alloy is processed by equal channel angular extrusion, microstructure is refined well due to heavy dynamic recrystallization occurring in severe plastic deformation.Compared with semisolid isothermal treatment and conventional SIMA, semisolid billet with fine and spheroidal grains are achieved in new SIMA.Thixoforging process of semisolid billet prepared by new SIMA has many advantages such as good surface quality of final component, high ability to fill cavity and net-shape.The fine and spheroidal grains and high mechanical properties such as tensile strength of 298 MPa and elongation of 28% can be developed in final part thixoforged.展开更多
An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface ar...An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significantly refined.In the center area of the copper,the grains are bigger than those at the boundary.On the surface of the deformable body,the grain size is the smallest,but with irregular grain morphology.After the product is entirely extruded,all the copper and aluminum grains are refined with small and uniform morphology.In the center area,the average diameter of aluminum grains is smaller than 5 μm,and the copper grain on the surface is about 10 μm.At the interface,the grain size is very small,with a good combination of copper and aluminum.The thickness of interface is in the range of 10-15 μm.Energy spectrum analysis shows that CuAl3 phase presents at the interface.展开更多
The microstructure and crystallographic texture characteristics of an extruded ZK60 Mg alloy subjected to cyclic extrusion and compression(CEC) up to 8 passes at 503 K were investigated.The local crystallographic text...The microstructure and crystallographic texture characteristics of an extruded ZK60 Mg alloy subjected to cyclic extrusion and compression(CEC) up to 8 passes at 503 K were investigated.The local crystallographic texture,grain size and distribution,and grain boundary character distributions were analyzed using high-resolution electron backscatter diffraction(EBSD).The results indicate that the microstructure is refined significantly by the CEC processing and the distributions of grain size tend to be more uniform with increasing CEC pass number.The fraction of low angle grain boundaries(LAGBs) decreases after CEC deformation,and a high fraction of high angle grain boundaries(HAGBs) is revealed after 8 passes of CEC.Moreover,the initial fiber texture becomes random during CEC processing and develops a new texture.展开更多
基金Project(311017)supported by the Major Projects of the Ministry of EducationProjects(51175335,51305261)supported by the National Natural Science Foundation of ChinaProject(2013M530194)supported by the Postdoctoral Science Foundation of China
文摘The visco-plastic self-consistent (VPSC) model is extended to take the dynamical recrystallization (DRX) into account so that the hot extrusion texture of AZ80 magnesium alloy can be properly modeled. The effects of extrusion temperatures and imposed boundary conditions on the resulting textures were investigated, and good agreement can be found between the simulated and the measured extrusion textures. The simulated results show that the DRX grains are responsible for the formation of the {2110} fiber component since the {1010} poles of the DRX grains are tilted away from those of the unrecrystallized grains during the formation of their high angle boundaries (HABs). Furthermore, the basal poles of the grains are favorably oriented to the transversal direction (TD) where the imposed deformation is larger due to lower slip resistance of the basal slip. The elevated temperature enhances the activity of pyramidal ?c+a? slip modes and gives rise to a larger recrystallized volume fraction, resulting in a weakened extrusion texture.
基金Project(2007CB613700)supported by National Basic Research Program of ChinaProject(2006BAE04B03)supported by Item of Support Plan during the 11th National Five-Year PlanProjects(CST,2007bb4413)supported by National Science Foundation of Chongqing,China
文摘Three-dimensional（3D） geometric models with different comer angles （90° and 120°） and with or without inner round fillets in the bottom die were designed. Some important process parameters were regarded as the calculation conditions used in DEFORMTM-3D software, such as stress--strain data of compression test for AZ31 magnesium, temperatures of die and billet, and friction coefficient. Influence of friction coefficient on deformation process was discussed. The results show that reasonable lubrication condition is important to plastic deformation. The change characteristics for distributions of effective stress and strain during an equal channel angular extrusion （ECAE） process with inner angle of 90° and without fillets at outer comer were described. Inhomogeneity index （C） was defined and deformation heterogeneity of ECAE was analyzed from the simulation and experiment results. The deformation homogeneity caused by fillets at outer comer increased compared with the die without fillets. The cumulated maximum strains decrease with increasing the fillets of outer comer in ECAE die and the inner comer angle. The analysis results show that better structures of ECAE die including appropriate outer comer fillet and the inner comer angle of 90° for the die can improve the strain and ensure plastic deformation homogenization to a certain extent. The required extrusion force drops with increasing the fillet made at outer comer in ECAE die. It is demonstrated that the prediction results are in good agreement with experiments and the theoretical calculation and the research conclusions in literatures.
基金Project(50605015) supported by the National Natural Science Foundation of ChinaProject(HITQNJS.2008.012) supported by Development Program for Outstanding Young Teachers in Harbin Institute of Technology,China+1 种基金Projects(20090460884,20080440849) supported by China Postdoctoral Science FoundationProject(LBH-Q08104) supported by the Postdoctoral Foundation of Heilongjiang Province,China
文摘Semisolid billet of AZ80 magnesium alloy was prepared by new strain induced melt activated (new SIMA) process and thixoforging experiment was performed.The results show that after as-cast AZ80 magnesium alloy is processed by equal channel angular extrusion, microstructure is refined well due to heavy dynamic recrystallization occurring in severe plastic deformation.Compared with semisolid isothermal treatment and conventional SIMA, semisolid billet with fine and spheroidal grains are achieved in new SIMA.Thixoforging process of semisolid billet prepared by new SIMA has many advantages such as good surface quality of final component, high ability to fill cavity and net-shape.The fine and spheroidal grains and high mechanical properties such as tensile strength of 298 MPa and elongation of 28% can be developed in final part thixoforged.
基金Project(60806006) supported by the National Natural Science Foundation of China
文摘An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significantly refined.In the center area of the copper,the grains are bigger than those at the boundary.On the surface of the deformable body,the grain size is the smallest,but with irregular grain morphology.After the product is entirely extruded,all the copper and aluminum grains are refined with small and uniform morphology.In the center area,the average diameter of aluminum grains is smaller than 5 μm,and the copper grain on the surface is about 10 μm.At the interface,the grain size is very small,with a good combination of copper and aluminum.The thickness of interface is in the range of 10-15 μm.Energy spectrum analysis shows that CuAl3 phase presents at the interface.
基金Projects(50674067,51074106) supported by the National Natural Science Foundation of ChinaProject(09JC1408200) supported by the Science and Technology Commission of Shanghai Municipality,China
文摘The microstructure and crystallographic texture characteristics of an extruded ZK60 Mg alloy subjected to cyclic extrusion and compression(CEC) up to 8 passes at 503 K were investigated.The local crystallographic texture,grain size and distribution,and grain boundary character distributions were analyzed using high-resolution electron backscatter diffraction(EBSD).The results indicate that the microstructure is refined significantly by the CEC processing and the distributions of grain size tend to be more uniform with increasing CEC pass number.The fraction of low angle grain boundaries(LAGBs) decreases after CEC deformation,and a high fraction of high angle grain boundaries(HAGBs) is revealed after 8 passes of CEC.Moreover,the initial fiber texture becomes random during CEC processing and develops a new texture.
