Homogeneous nucleation of dislocation loops in nanocrystalline metals and ceramics

A special mechanism of dislocation nucleation in deformed nanocrystalline metals and ceramics is theoretically described. The mechanism represents non-local homogeneous nucleation of a nanoscale loop of “non-crystallographic” partial dislocation whose Burgers vector magnitude continuously grows during the nucleation process. The dislocation loop nucleation is accompanied by nucleation and evolution of a generalized stacking fault bounded by the loop. It is shown that the special mechanism can effectively produce nanoscale loops of lattice dislocations in nanocrystalline metals (Al, Ni) and ceramics (3C–SiC) deformed at high mechanical stresses achieved in shock-wave and indentation load regimes.