Dislocations emitted from nanocrystalline grain boundaries: nucleation and splitting distance

The nucleation and propagation of dissociated full dislocations from grain boundaries in nanocrystalline fcc metals is discussed in terms of the splitting distance between two partial dislocations. It is demonstrated that the use of the splitting distance assumes the existence of the partial dislocations and therefore can not account for nucleation criteria. Moreover, even once both partial dislocations are nucleated, the local stress distribution seems to play an important role in the separation of the partials.