Influence of irradiation damage on slip transfer across grain boundaries

The interaction of lattice dislocations with grain boundaries in proton- and ion-irradiated austenitic stainless steels is investigated. At the macroscale, interactions of dislocation channels with grain boundaries result in slip blockage, slip transmission and slip along the grain boundary with an associated in-plane displacement. At the dislocation level, slip transmission prediction is governed by the strain energy density minimization. However, the importance of the local resolved shear stress increases, in the sense that it must be of sufficient magnitude to propagate the dislocations through the damaged matrix. If this condition is not satisfied, the grain boundary will activate an alternative mechanism to relieve the strain accumulated from accommodation of lattice dislocations and the stress concentration associated with the formation of a dislocation pile-up. One observed relief mechanism involves the nucleation and propagation of a crack along the grain boundary, which is accompanied by an out-of-plane displacement of the boundary.