The mixed yield surfaces of fcc single crystals for slip on ｛111｝〈110〉 and mechanical twinning on ｛111｝〈112〉 systems have been derived when their critical resolved shear stresses are equal. It has been found t...The mixed yield surfaces of fcc single crystals for slip on ｛111｝〈110〉 and mechanical twinning on ｛111｝〈112〉 systems have been derived when their critical resolved shear stresses are equal. It has been found that there are 259 stress states that can be classified into 21 groups according to the crystal symmetry. Each group activates 5, 6 or 8 slip or/and twinning systems depending on crystallographically non equivalent slip or/and twinning systems groups. Among all those stress states, 3 groups activate 8 systems, including 21 stress states; 9 groups activate 5 systems, including 70 ones; the remaining 9 groups activate 5 systems, including 168 ones.展开更多
Some applications of crystal plasticity modeling in equal channel angular extrusion（ECAE） of face-centered cubic metals were highlighted.The results show that such simulations can elucidate the dependency of grain r...Some applications of crystal plasticity modeling in equal channel angular extrusion（ECAE） of face-centered cubic metals were highlighted.The results show that such simulations can elucidate the dependency of grain refinement efficiency on processing route and the directionality of substructure development,which cannot be explained by theories that consider only the macroscopic deformation behavior.They can also capture satisfactorily the orientation stability and texture evolution under various processing conditions.It is demonstrated that crystal plasticity models are useful tools in exploring the crystallographic nature of grain deformation and associated behavior that are overlooked or sometimes erroneously interpreted by existing phenomenological theories.展开更多
An experimental study of the microstructures in pure copper billets processed by 8 passes of equal channel angular extrusion （ECAE） via an extended range of processing routes with a 90° die is carried out. Each...An experimental study of the microstructures in pure copper billets processed by 8 passes of equal channel angular extrusion （ECAE） via an extended range of processing routes with a 90° die is carried out. Each processing route is defined according to the inter-pass billet rotation angle （χ）, which varies from 0° to 180°. According to the generation of high-angle boundaries and reduction of grain size by electron backscatter diffraction （EBSD） measurements, the grain refinement is found to be most efficient for route with χ=90°and least efficient with χ=180°, among the seven routes studied. This trend is supported by supplementary transmission electron microscopy （TEM） measurements. Comparison of the EBSD and TEM data reveals the importance of considering the non-equiaxity of grain structures in quantitative assessment of microstructural differences in ECAE-processed materials.展开更多
文摘The mixed yield surfaces of fcc single crystals for slip on ｛111｝〈110〉 and mechanical twinning on ｛111｝〈112〉 systems have been derived when their critical resolved shear stresses are equal. It has been found that there are 259 stress states that can be classified into 21 groups according to the crystal symmetry. Each group activates 5, 6 or 8 slip or/and twinning systems depending on crystallographically non equivalent slip or/and twinning systems groups. Among all those stress states, 3 groups activate 8 systems, including 21 stress states; 9 groups activate 5 systems, including 70 ones; the remaining 9 groups activate 5 systems, including 168 ones.
基金Projects(50871040,51271204) supported by the National Natural Science Foundation of ChinaProject(2012CB619500) supported by the National Basic Research Program of ChinaProject(NCET-06-0741) supported by the Program for New Century Excellent Talents, China
文摘Some applications of crystal plasticity modeling in equal channel angular extrusion（ECAE） of face-centered cubic metals were highlighted.The results show that such simulations can elucidate the dependency of grain refinement efficiency on processing route and the directionality of substructure development,which cannot be explained by theories that consider only the macroscopic deformation behavior.They can also capture satisfactorily the orientation stability and texture evolution under various processing conditions.It is demonstrated that crystal plasticity models are useful tools in exploring the crystallographic nature of grain deformation and associated behavior that are overlooked or sometimes erroneously interpreted by existing phenomenological theories.
基金Project(50871040)supported by the National Natural Science Foundation of ChinaProject(NCET-06-0741)supported by the Program for New Century Excellent Talents of China
文摘An experimental study of the microstructures in pure copper billets processed by 8 passes of equal channel angular extrusion （ECAE） via an extended range of processing routes with a 90° die is carried out. Each processing route is defined according to the inter-pass billet rotation angle （χ）, which varies from 0° to 180°. According to the generation of high-angle boundaries and reduction of grain size by electron backscatter diffraction （EBSD） measurements, the grain refinement is found to be most efficient for route with χ=90°and least efficient with χ=180°, among the seven routes studied. This trend is supported by supplementary transmission electron microscopy （TEM） measurements. Comparison of the EBSD and TEM data reveals the importance of considering the non-equiaxity of grain structures in quantitative assessment of microstructural differences in ECAE-processed materials.
