Roles of grain boundary and dislocations at different deformation stages of nanocrystalline copper under tension

The plastic deformation of nanocrystalline copper subjected to tension has been studied using molecular dynamics simulation. The results show that, in the initial stage, the deformation is mainly boundary-mediated in small grains; while in the late stage, the deformation is accommodated by dislocations in large grains. It is also found that the stress-assisted grain growth occurs owing to atomic diffusion and grain boundary migration. These results are consistent with recent experimental observations.