Dislocation glide in model Ni(Al) solid solutions by molecular dynamics

The glide of an edge dislocation, in a random solid solution, Ni (1 to 8 at % Al), is simulated by molecular dynamics (MD). An embedded atom method potential has been optimized to reproduce the relevant properties of the face centered cubic solid solution and of the L12 Ni3Al phase. Glide is studied at fixed temperature and applied stress. Three parameters are found to be necessary to describe the rate of shear as a function of applied shear stress: σs is the static threshold stress, below which the glide distance of the dislocation is not sufficient to insure sustained shearing; σd is the dynamical threshold stress, which reflects the friction of the pinning potential on the moving dislocation; B is the friction coefficient, which relates the effective stress (σ−σd) to the glide velocity. We also find that the obstacles are made of specific configurations of the Al atoms, which are brought in positions of strong mutual repulsion in course of the glide process. The solute-solute short range repulsion, rather than the usually assumed dislocation-solute interaction, is thus argued to be the main mechanism responsible for chemical hardening in the present concentrated random solid solution. The use of the above results in the frame of multi-scale modeling is exemplified.