Invited Lecture
Simulating dislocation-solute co-evolution in body-centered cubic metals on diffusive timescales

The interaction between solute atoms and dislocations is behind numerous mechanical behavior processes of great importance in materials science. In addition to solution hardening and/or softening, solutes may also dynamically evolve around dislocation cores, giving rise to important phenomena such as the formation of solute clouds, jerky flow, dynamic strain aging, etc. Typically, dislocation-solute interactions are modeled in the two extremes of the adiabatic approximation where either dislocations or solutes are stationary on the timescale of motion of the other. While this can give insight into processes such as solid solution strengthening or solute could formation, it cannot capture dynamic effects where both subpopulations evolve on comparable timescales. In addition, in body-centered cubic alloys, plastic flow is generally controlled by the thermally activated motion of screw dislocations, which proceeds by nucleation and propagation of kinks along the dislocation line. As such, solute-dislocation interactions must be dealt with in a manner consistent with this intrinsic behavior. In this work, we present a kinetic Monte Carlo model where solute hopping and kink-pair nucleation/motion are part of a unified framework where both subspecies evolve concurrently and are coupled by bidirectional elastic and inelastic interactions. The coupling is done by calculating the elastic dipole tensors using electronic structure calculations, as well as by obtaining inelastic interaction energies between dislocation cores and solute atoms. We use the parameterized model to predict the hardening-softening transition in W-Re alloys and to capture the conditions under which dynamic strain aging might be expected in W-O alloys.