Grain boundary migration as rotational deformation mode in nanocrystalline materials

Stress-induced grain boundary migration is theoretically described as a new mode of rotational plastic deformation in nanocrystalline materials. We have calculated the strain energy change due to migration of a grain boundary that carries rotational plastic flow. It is shown that, depending on the stress level, the grain boundary can either be immobile or mobile, and in the latter case it can migrate in either a stable or unstable regime. The critical stress values, which correspond to the transitions between these migration regimes, are estimated and discussed.