Section 10. Fundamentals of defects and radiation effects in materials Mechanisms of dislocation-defect interactions in irradiated metals investigated by computer simulations

During irradiation, mobile defects, defect clusters and impurity atoms segregate on dislocations. When an external stress is applied, plastic flow is initiated when dislocations are unlocked from segregated defects. Sustained plasticity is achieved by continuation of dislocation motion, overcoming local forces due to dispersed defects and impurities. The phenomena of flow localization, post-yield hardening or softening and jerky flow are controlled by dislocation-defect interactions. We review here computational methods for investigations of the dynamics of dislocation-defect interactions. The influence of dislocations on the motion of glissile self-interstitial atoms (SIAs) and their clusters is explored by a combination of kinetic Monte Carlo and dislocation dynamics. We show that dislocation decoration by SIAs is a result of their 1-D motion and rotation as they approach dislocation cores. The interaction between dislocations and immobilized SIA clusters indicates that the unlocking mechanism is dictated by shape instabilities. Finally, computer simulations for the interaction between freed dislocations and stacking fault tetrahedra in irradiated Cu, and between dislocations and microvoids in irradiated iron are presented, and the results show good agreement with experimental observations.