Dislocation loop evolution from a source in a field of randomly distributed uniform obstacles

Abstract

We have created a computer simulation of dislocation loop emission by a Frank-Read source and its evolution in a uniform field of randomly distributed, weak, point obstacles. We discovered a threshold source length such that dislocation loops from shorter sources expand in a super-obstacle regime; otherwise they enlarge by thermal activation, and there is a relationship to the strength of the obstacle. We determine the range of stresses in which dislocation loops expand above the obstacle, shrink, or grow via thermal activation. In contrast with infinite linear dislocations, we do not observe stable evolution (i.e., velocity and other characteristics) of dislocation loops in all stress regimes.