The glide of an edge dislocation in a random solid solution, Ni (1 to 8at%Al), was simulated by molecular dynamics. An embedded atom method potential was optimized so as to reproduce the relevant properties of the face centered cubic solid solution and of the L12 Ni3Al phase. Glide was studied at a fixed temperature and applied stress. Three parameters were found to be necessary in order to describe the rate of shear as a function of the applied shear stress, σs. This was the static threshold stress below which the glide distance of the dislocation was insufficient to ensure sustained shearing. Also, σd was the dynamic threshold stress, which reflected the frictional effect of the pinning potential upon the moving dislocation. The friction coefficient related the effective stress, (σ – σd), to the glide velocity. It was found that the obstacles were made up of specific configurations of Al atoms, which were brought into positions of strong mutual repulsion during glide. Solute-solute short-range repulsion, rather than the usually assumed dislocation-solute interaction, was suggested to be the main mechanism which was responsible for chemical hardening in concentrated random solid solutions.

Dislocation Glide in Model Ni(Al) Solid Solutions by Molecular Dynamics. E.Rodary, D.Rodney, L.Proville, Y.Bréchet, G.Martin: Physical Review B, 2004, 70[5], 054111 (11pp)