Softening effects due to reorientations of Cu precipitates in α -iron: Atomistic simulations of dislocations-obstacles interactions

Abstract

Radiation-induced hardening by precipitates, which essentially has a dislocation pinning effect, is a major issue in nuclear reactor pressure vessels research. In this study, simulations of interactions between edge dislocations and copper precipitates are conducted as an example to investigate size-dependent pinning effects. Using molecular dynamics simulations, we discover a new two-stage mechanism that includes the processes of reorientations and atomistic collective migrations during the interactions. Both of these result in a weakening of the pinning effect on dislocations when the phase transition occurs in copper precipitates, which can be reflected in the decrease of the critical shear stress in stress and strain curves. Our studies considered the atomistic arrangement of the obstacle during the interaction, which constructively provide a new perspective for research studies of dislocation-obstacle pinning interaction and offer a more comprehensive estimation on the pinning strength of dislocations.