3D dislocation dynamics study of plastic instability in irradiated copper

Abstract

The onset of plastic instability in neutron irradiated copper is investigated by computer simulation of the dynamics of the elastic interaction between dislocation loops emitted from Frank–Read (F–R) sources and irradiation-induced defect clusters. We show that small prismatic defect clusters produced directly from collision cascades are trapped in the stress field of slip dislocations, and that mobile clusters are absorbed in the dislocation core, when they approach within ∼6 nm. Sessile vacancy clusters are also absorbed within this ‘stand-off’ distance because of an induced surface tension on their stacking fault. The interaction between prismatic defect clusters in ‘decorations’ and dislocations is shown to provide significant resistance to the initiation of plastic deformation in irradiated copper (source hardening). Sessile stacking fault tetrahedra are also shown to resist dislocation motion by localized forces before they are absorbed and removed by activated dislocation sources. The significance of these mechanisms to initiation of localized deformation and plastic instability are discussed.