Molecular dynamics simulation of core structure of (c+a) edge dislocations in slip deformation of hcp metals

To understand the deformation mechanism due to non-basal slip in hcp metals, the core structure of edge dislocation with Burgers vector (c + a) was investigated by molecular dynamics simulation using a Lennard-Jones type pair potential. A perfect (c + a) edge dislocation was introduced along F [1 (1) over bar 00] direction at the center of the model crystal. In the case of [0001] tensile, a core structure of the (c + a) perfect edge dislocation (Type-A) changed into {1 (2) over bar 11} twin-like structure with increasing strain. The Type-A moves at the tensile stress of 6.8 GPa with twin structure. The (c + a) edge dislocation consisted with two partial dislocations (Type-B) moves along (11 (2) over bar2) plane with increasing strain. The critical tensile stress of the Type-B was about 3.4 GPa. In the case of [0001] compression, although the both type of dislocations moved in the opposite direction as the Type-B, the critical stress in compression was smaller than that in the tensile. This explains how the mobility of (c + a) edge dislocations seen in our tensile tests depends on the direction of applied stress. A temperature dependence of the critical stress has been demonstrated, so that when the temperature was raised from 0 K to 30 K, the stress decreased rapidly in all case.