美国西北大学和博伊斯州立大学（Boise State University）的研究人员已生产出一种镍-锰-镓多晶合金，当暴露在磁场中时，该合金改变形状。当磁场关闭后，该合金保持其新形状，但是，如果将磁场旋转90度，合金又回复其原形状，说明其有...美国西北大学和博伊斯州立大学（Boise State University）的研究人员已生产出一种镍-锰-镓多晶合金，当暴露在磁场中时，该合金改变形状。当磁场关闭后，该合金保持其新形状，但是，如果将磁场旋转90度，合金又回复其原形状，说明其有“磁形状记忆”功能。展开更多
A polycrystal plasticity model was developed to analyze the room-temperature deformation behaviors of Mg-3A1-1Zn alloy（AZ31）.The uniaxial tension and compression tests at room temperature were conducted using cast a...A polycrystal plasticity model was developed to analyze the room-temperature deformation behaviors of Mg-3A1-1Zn alloy（AZ31）.The uniaxial tension and compression tests at room temperature were conducted using cast and extruded AZ31 rods with different textures and combined with the proposed model to reveal the deformation mechanisms.It is shown that,different flow curves of two specimens under tension and compression tests can be simulated by this model.The flow curves of AZ31 extrusions exhibit different shapes for tension and compression due to different activities of tensile twinning and pyramidalc＋a slip.The metallographic and TEM observations showed the equal twinning activities at the initial stage in tension and compression tests and the occurrence of pyramidalc＋a slip in compression of as-cast Mg-3A1-1Zn alloy with increasing the strain,which is consistent with the simulated results by the proposed model.展开更多
Rapidly solidified Fe100-xGax （x=16-20） alloy rods were prepared by induction melting and copper mold casting under the protection of inert gases. The optical microscopy observation shows that the large and elongate...Rapidly solidified Fe100-xGax （x=16-20） alloy rods were prepared by induction melting and copper mold casting under the protection of inert gases. The optical microscopy observation shows that the large and elongated columnar grains grow along the radial direction, which is parallel to the temperature gradient direction. The preferred orientation texture along the axial direction of the rod was detected by XRD. With the increase of Ga content, the saturation magnetization （Ms） of the alloys decreases distinctly and the dynamic response in low magnetic field increases drastically, the maximum longitudinal saturation magnetostriction for as-cast Fe82Ga18 alloy rods is 92×10-6 under an applied magnetic field strength of 30 kA/m. The large magnetostriction of Fe100-xGax alloys is attributed to the rapidly solidified disordered A2 phase and the high concentration of short range order of Ga atom clusters, which are arranged in the direction and finally trigger the formation of modified-DO3 structure, just as shown by the split of the （200） diffraction peak. Ordered DO3 phase is not conducive to the magnetostriction.展开更多
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
Microscopy, X ray diffractometry and EBSD analysis were applied to inspect the relationships between deformation mechanisms and initial textures in polycrystalline magnesium alloys AZ31. It is found that different def...Microscopy, X ray diffractometry and EBSD analysis were applied to inspect the relationships between deformation mechanisms and initial textures in polycrystalline magnesium alloys AZ31. It is found that different deformation mechanisms proceed according to theoretic prediction. Basal slips occur when basal planes of grains are tilted toward normal direction(ND) around transverse direction(TD); prism slips dominate when basal planes are perpendicular to TD. {1012} twinning was favored when basal planes are normal to rolling direction(RD) and {1011} twinning is analyzed to be related to the basal orientation of grains.展开更多
基金Project(51201092)supported by the National Natural Science Foundation of China
文摘A polycrystal plasticity model was developed to analyze the room-temperature deformation behaviors of Mg-3A1-1Zn alloy（AZ31）.The uniaxial tension and compression tests at room temperature were conducted using cast and extruded AZ31 rods with different textures and combined with the proposed model to reveal the deformation mechanisms.It is shown that,different flow curves of two specimens under tension and compression tests can be simulated by this model.The flow curves of AZ31 extrusions exhibit different shapes for tension and compression due to different activities of tensile twinning and pyramidalc＋a slip.The metallographic and TEM observations showed the equal twinning activities at the initial stage in tension and compression tests and the occurrence of pyramidalc＋a slip in compression of as-cast Mg-3A1-1Zn alloy with increasing the strain,which is consistent with the simulated results by the proposed model.
基金Project (11004091) supported by the National Natural Science Foundation of ChinaProject (Y4090219) supported by the Natural Science Foundation of Zhejiang Province, China+1 种基金Project (0916RJZA025) supported by the Natural Science Foundation of Gansu Province, ChinaProject (Q201104) supported by the "Hongliu Outstanding Youth" Foundation of Lanzhou University of Technology, China
文摘Rapidly solidified Fe100-xGax （x=16-20） alloy rods were prepared by induction melting and copper mold casting under the protection of inert gases. The optical microscopy observation shows that the large and elongated columnar grains grow along the radial direction, which is parallel to the temperature gradient direction. The preferred orientation texture along the axial direction of the rod was detected by XRD. With the increase of Ga content, the saturation magnetization （Ms） of the alloys decreases distinctly and the dynamic response in low magnetic field increases drastically, the maximum longitudinal saturation magnetostriction for as-cast Fe82Ga18 alloy rods is 92×10-6 under an applied magnetic field strength of 30 kA/m. The large magnetostriction of Fe100-xGax alloys is attributed to the rapidly solidified disordered A2 phase and the high concentration of short range order of Ga atom clusters, which are arranged in the direction and finally trigger the formation of modified-DO3 structure, just as shown by the split of the （200） diffraction peak. Ordered DO3 phase is not conducive to the magnetostriction.
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.
文摘Microscopy, X ray diffractometry and EBSD analysis were applied to inspect the relationships between deformation mechanisms and initial textures in polycrystalline magnesium alloys AZ31. It is found that different deformation mechanisms proceed according to theoretic prediction. Basal slips occur when basal planes of grains are tilted toward normal direction(ND) around transverse direction(TD); prism slips dominate when basal planes are perpendicular to TD. {1012} twinning was favored when basal planes are normal to rolling direction(RD) and {1011} twinning is analyzed to be related to the basal orientation of grains.
