Atomistic study of the generation, interaction, accumulation and annihilation of cascade-induced defect clusters

Recent theoretical calculations and atomistic computer simulations have shown that glissile clusters of self-interstitial atoms (SIAs) play an important role in the evolution of microstructure in metals and alloys under cascade damage conditions. Over the past decade or so, the properties of SIA clusters in fcc, bcc and hcp lattices have been widely studied. In this paper we review key properties of these defects and also those of vacancy clusters formed directly in cascades, and present an atomic-level picture based on computer modelling of how these properties may change in the presence of other defects, impurities, stress fields, etc. We then examine the role of cluster properties and the consequences of their interactions in the process of damage accumulation and changes in mechanical and physical properties. We focus on the formation of defect clusters (e.g. dislocation loops and stacking fault tetrahedra (SFT)) and their segregation in the form of rafts of dislocation loops and atmospheres of loops decorating dislocations. Finally, we address the problem of radiation hardening by considering interactions between mobile dislocations and defect clusters (e.g. SIA dislocation loops, SFT and microvoids) produced during irradiation.