A theoretical model was proposed in order to describe the emission of lattice and grain-boundary dislocations from pores in nanocrystalline metals during mechanical loading. In this model, dislocation emission occurred via an ideal nanoshear. A dislocation nucleated at a finite distance from a pore, and the modulus of its Burgers vector increased continuously from zero to the modulus of the Burgers vector of a lattice or grain-boundary dislocation. The applied stress and the critical pore-dislocation distance were determined at which dislocation emission via an ideal nanoshear in nanocrystalline Ni, Al, and Cu became an energetically favourable and barrier-free process.

Dislocation Emission by Pores in Nanocrystalline Metals. S.V.Bobylev, N.F.Morozov, I.A.Ovidko: Physics of the Solid State, 2007, 49[6], 1098-103