Dislocation motion in tungsten: Atomistic input to discrete dislocation simulations

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/2111 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 experim entally 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.