Multiscale modelling of plastic flow localization in irradiated materials

The irradiation of metals by energetic particles causes significant degrada tion of the mechanical properties(1,2), most notably an increased yield str ess and decreased ductility, often accompanied by plastic flow localization . Such effects limit the lifetime of pressure vessels in nuclear power plan ts(3), and constrain the choice of materials for fusion-based alternative e nergy sources(4). Although these phenomena have been known for many years(1 ), the underlying fundamental mechanisms and their relation to the irradiat ion field have not been clearly demonstrated. Here we use three-dimensional multiscale simulations of irradiated metals to reveal the mechanisms under lying plastic flow localization in defect-free channels. We observe disloca tion pinning by irradiation-induced clusters of defects, subsequent unpinni ng as defects are absorbed by the dislocations, and cross-slip of the latte r as the stress is increased. The width of the plastic flow channels is lim ited by the interaction among opposing dislocation dipole segments and the remaining defect clusters.