Computer simulation of dislocation cores in h.c.p. metals III. The effect of applied shear strain

Abstract

The influence of applied glide strain on the dislocation cores simulated in part II has been investigated, and the critical strains for glide determined. Only one of the four model crystals mimics basal-slip by having a much lower critical strain for 〈1120〉(0001) glide than 〈1120〉{1200} glide, and this is found to be due to the core structure of the screw dislocation. In the crystal in which core disregistry extends on {1100}, prism slip is much easier, but the edge dislocation is cracked and sessile. Plasticity associated with the dislocations with Burgers vector ⅓〈1123〉 is complicated and dependent in form on the interatomic potential and sense of shear. Nevertheless, it is clear that under shear corresponding to [0001] tension, the edge is generally associated with either {1121} twinning or {1122} slip, whereas under the opposite shear it produces either {1122} slip or {1122} twinning. Under the former shear, the screw glides on either {101} or {1122}, the choice depending on the crystal potential but not on the unstrained core state. The slip geometry is reversed when the sense of shear is reversed. The results are discussed in relation to plasticity in real metals and the γ-surface studied in part I.