Direct prediction of the solute softening-to-hardening transition in W-Re alloys using stochastic simulations of screw dislocation motion

摘要

Interactions among dislocations and solute atoms are the basis of severalimportant processes in metals plasticity. In body-centered cubic (bcc) metalsand alloys, low-temperature plastic flow is controlled by screw dislocationglide, which is known to take place by the nucleation and sideward relaxationof kink pairs across two consecutive \emph{Peierls} valleys. In alloys,dislocations and solutes affect each other's kinetics via long-range stressfield coupling and short-range inelastic interactions. It is known that incertain substitutional bcc alloys a transition from solute softening to solutehardening is observed at a critical concentration. In this paper, we develop akinetic Monte Carlo model of screw dislocation glide and solute diffusion insubstitutional W-Re alloys. We find that dislocation kinetics is governed bytwo competing mechanisms. At low solute concentrations, nucleation is enhancedby the softening of the Peierls stress, which overcomes the elastic repulsionof Re atoms on kinks. This trend is reversed at higher concentrations,resulting in a minimum in the flow stress that is concentration and temperaturedependent. This minimum marks the transition from solute softening tohardening, which is found to be in reasonable agreement with experiments.