Dislocation motion in tungsten: Atomistic input to discrete dislocation simulations

Abstract

A computational framework for the discrete dislocation dynamics simulation of body-centered cubic (bcc) metals which incorporates atomistic simulation results is developed here on the example of tungsten. Mobility rules for the a/2〈111〉 screw dislocations are based on the kink-pair mechanism. The fundamental physical quantity controlling the kink-pair nucleation, the stress-dependent activation enthalpy, is obtained by fitting the line-tension model to atomistic data extending the approach by Gröger et al. (2008a,b) and Gröger and Vitek (2008c). In agreement with atomistic simulation, kink-pair nucleation is assumed to occur only on {110} planes. It is demonstrated that slip of the crystal along high-index planes like {112} which is often observed in experiments is obtained by the glide of the dislocation on two or more {110} planes. It is shown that such an atomistic based description of the dislocation mobility provides a physical basis to naturally explain many experimentally observed phenomena in bcc metals like the tension–compression asymmetry, the orientation dependence of loading, temperature dependence of yield stress and the crystallography of slip.