Synergy of grain boundary sliding and shear-coupled migration process in nanocrystalline materials

An attempt has been made to illustrate a new physical mode of plastic deformation in nanocrystalline materials that synergizes two processes, i.e. grain boundary (GB) sliding and stress-driven shear-coupled GB migration. The latter process incorporates a rotational and a translational plastic flow, in which a normal migration is coupled with a shear. The energy change resulting from the above-mentioned mode was calculated, and showed that the new deformation mode was much more energetically favorable than both the pure GB sliding mode and the cooperative process of GB sliding and migration without a coupling shear. In addition, the new deformation mode considerably enhances the ductility of nanocrystalline materials compared with the other two above-mentioned processes.