Anomalous multiplication of lattice dislocations at grain boundaries in nanocrystalline solids

A new physical micromechanism for anomalous multiplication of lattice dislocations in nanocrystalline solids at ultrahigh stresses is suggested and theoretically described. The new micromechanism represents the ultrahigh-stress-driven splitting of a gliding grain boundary (GB) dislocation into two gliding lattice dislocations and a sessile GB dislocation. Our theory is consistent with the experimental data (Wang et al 2006 Appl. Phys. Lett. 88 061917) on observation of high-density ensembles of dislocations in nanocrystalline nickel after laser-driven deformation. (paper)