Non-homogeneous deformation behavior in nanocrystalline materials based on grain rotation

HAN Xue-ping， ZHOU Jian-qiu
（College of Mechanical and Power Engineering， Nanjing University of Technology， Nanjing 210009， China）

Abstract： The formation and development of shear band are the main reason for the non-homogeneous deformation，low ductility and premature failure of nanocrystalline materials. In order to study the nature of shear band，based on a grain rotation theory of diffusion-accommodated grain boundary sliding，an evolution model of shear band was established. The effect of grain orientation and grain size on evolution of shear band was investigated. In the model，the grains were divided into soft-grains within shear bands and hard-grains without shear bands according to the differences between grain orientation and shear orientation. Under the grain rotation，more and more grains become soft-grains and the size and overall volume fraction of shear bands were changed with the loading of materials. The results show that as the increasing of plastic strain，the volume fraction of shear bands general increases for all grain clusters with different mean maximum Schmid factors，the volume fraction of shear bands is inverse ratio to grain size. The larger the grain size，the smaller the volume fraction of the shear zone.
Key words： nanocrystalline materials； grain rotation； shear band； deformation behavior