Dislocation motion in the presence of diffusing solutes: a computer simulation study

A discrete lattice, kinetic Monte Carlo model is developed to simulate the motion of an edge dislocation in the presence of interacting, diffusing solute atoms that have a misfit with respect to the matrix. The simulation self-consistently determines the solute concentration profile (in two spatial dimensions), as well as the associated dislocation velocity. The solute segregation profile around the moving dislocation is characterized at low velocity by a condensed solute cloud near and on one side of the dislocation core, a region depleted of solute on the opposite side and a diffuse solute (Cottrell) atmosphere further from the core. At high velocity, no condensed solute cloud forms. The relation between the dislocation velocity and the applied stress shows a low-velocity, solute drag branch and a high-velocity branch, typified by no solute cloud but with occasional solute trapping. At intermediate velocities, the dislocation stochastically jumps between these two branches.