Published online by Cambridge University Press: 15 February 2011
Discrete dislocation dynamics simulations have been performed to study dislocation activity in the vicinity of a crack tip and to get a better understanding of the decisive mechanisms of the brittle-to-ductile transition (BDT). The comparison of these simulations with fracture experiments on tungsten single crystals leads to a preliminary model for the BDT of this material. Many features predicted by this model are also found in other materials. Dislocation nucleation and the availability of active sources are shown to be limiting plasticity at low temperatures and partly in the semi-brittle regime. At elevated temperatures dislocation nucleation occurs easily, such that plasticity in this regime and the BDT itself, must be viewed as a thermally activated processes, which are controlled by dislocation mobility.