Clusters of self-interstitial atoms were formed in metals by high-energy displacement cascades, often in the form of small dislocation loops with a perfect Burgers vector. In isolation, they were able to undergo fast, thermally activated glide in the direction of their Burgers vector, but did not move in response to a uniform stress field. The present work considers their ability to glide under the influence of the stress of a gliding dislocation. If loops could be dragged by a dislocation, it would have consequences for the effective cross-section for dislocation interaction with other defects near its glide plane. The lattice resistance to loop drag cannot be simulated accurately by the elasticity theory of dislocations, so here it was investigated in Fe and Cu by atomic-scale computer simulation. It was shown that a row of loops lying within a few nanometres of the dislocation slip plane could be dragged at very high speed. The drag coefficient associated with this process was determined as a function of metal, temperature and loop size and spacing. A model for loop drag, based on the diffusivity of interstitial loops, was presented. It was tested against data obtained for the effects of drag on the stress to move a dislocation and the conditions under which a dislocation breaks away from a row of loops.

A Model for the Dynamics of Loop Drag by a Gliding Dislocation. Z.Rong, Y.N.Osetsky, D.J.Bacon: Philosophical Magazine, 2005, 85[14], 1473-93