A simple dislocation model of the influence of high-angle boundaries on the deformation behavior of ultrafine-grained materials

The deformation resistance of ultrafine-grained (UFG) materials is modelled on the basis of the evolution of the average dislocation density with strain in the course of glide and recovery of dislocations. In contrast to materials with conventional grain size (CG), dislocations are stored and annihilated solely at the high-angle boundaries, where screw dislocations glide and edge dislocations climb towards annihilation sites. The high-angle boundaries enhance both the rates at which dislocations are stored and recovered. Depending on the spacing of high-angle boundaries, temperature and strain rate, UFG materials are softer or harder than their CG counterparts.