Atomic features of the interaction between a screw dislocation and self-interstitial atoms in model iron and vanadium lattices.

Abstract

The interaction between a screw dislocation and self-interstitial atoms (SIA's) in iron and vanadium lattices under applied shear stress has been investigated by computer simulation using Johnson-Wilson potentials for iron and vanadium. Two structures of SIA, i.e., a dumbbell and a crowdion have been taken into account. Although the former is stable in the matrix, the crowdion is more stable than the dumbbell in a screw dislocation core. On the encounter of a gliding screw dislocation with a SIA (dumbbell type), conversion from the dumbbell to the crowdion occurred in a screw dislocation core, resulting in the formation of three kink configuration. These kinks propagated along a dislocation line under shear stress. This greatly contributes to the understanding of irradiation softening observed in iron single crystals after low temperature irradiation. The interaction between a screw dislocation and di-interstitial atoms was simulated in the case of vanadium and also contributed to the irradiation softening.