Temperature dependent deformation localization in irradiated tungsten

Abstract

Tungsten is considered as the plasma-facing material in the nuclear fusion device, which has to withstand coupled irradiation, mechanical and thermal conditions. To guarantee the safe operation of energy devices, it is essential to accurately predict its response. As a typical body center cubic material, the plasticity of tungsten is believed to exhibit the strong temperature dependence and non-Schmid effect. It is far from well understood how these plasticity features influence the behavior of irradiated tungsten. To disclose this mystery, a crystal plasticity model is developed, which considers the kink-pair mechanism of screw dislocations, the contribution of edge dislocations, and the interaction between dislocations and irradiation defects. The model is firstly verified through comparing with the available experimental results at different temperatures, and then used to disclose the temperature dependence of deformation localization in irradiated tungsten. It is found that post-irradiation mechanical tests at room temperature underestimate the occurrence of dislocation channel and deformation localization at higher temperatures, while in the low temperature regime, the thermal-activated dislocation mobility law may lead to a short-term deformation localization without clear dislocation channels. Conditions for the localization of deformation in irradiated tungsten are discussed, which is hoped to guide the reliable design of tungsten components used in fusion and fission reactors.