The deformation resistance of ultrafine-grained materials was 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, dislocations were 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 were stored and recovered. Depending on the spacing of high-angle boundaries, temperature and strain rate, ultrafine-grained materials were softer or harder than their conventional grain size counterparts.

A Simple Dislocation Model of the Influence of High-Angle Boundaries on the Deformation Behavior of Ultrafine-Grained Materials. W.Blum, P.Eisenlohr: Journal of Physics - Conference Series, 2010, 240[1], 012136