Numerical investigation of the brittle-to-ductile transition temperature of rolled high-purity tungsten

With increasing temperature, high-purity tungsten typically shows a sharp transition from fully brittle behaviour to a significantly more ductile response. The brittle-to-ductile transition of tungsten is not an invariant property, but depends on the microstructure and loading conditions. In the current work, this relation is investigated numerically. To this end, a crystal plasticity framework is adopted, combined with a newly proposed cleavage criterion. The crystal plasticity parameters are identified from experimental data, obtained from tensile tests on rolled polycrystalline samples. The brittle-to-ductile transition is subsequently examined for different strain rates, which allows for calculating the activation energy of the brittle-to-ductile transition. The resulting activation energy is in adequate agreement with experimental findings in literature. Finally, different loading directions with respect to the anisotropic microstructure are considered. The numerically obtained transition temperatures in these directions are consistent with experimental data. The proposed model is therefore instrumental for improving the design of the tungsten monoblocks for future fusion reactors.