A mechanism for the sweeping-up of loops by glide dislocations during deformation

Abstract

Dislocation loops in irradiated or quenched metal crystals are swept out by the glide dislocations during deformation, leaving cleared channels. The removal of prismatic loops with the same Burgers vector as the glide dislocations can occur by direct recombination (Saada and Washburn 1963) but the annihilation of loops with Burgers vector out of the glide plane has not been explained. A simple mechanism is proposed for their removal in face-centred cubic crystals. This involves the formation of a junction around half the loop followed by the gliding together and coalescence of this with the other half. Both steps are glissile and energetically favourable, and give complete annihilation of the loop at the expense of a change in shape of the glide dislocation. Faulted loops may also be removed in this way if they first unfault in the presence of a glide dislocation. The mechanism is not diffusion controlled, but requires a high loop mobility and may be affected by impurity pinning.