Plastic deformation in advanced tungsten-based alloys for fusion applications studied by mechanical testing and TEM

Abstract

In this work, we have assessed mechanical properties of several tungsten grades considered as perspective materials for applications in plasma facing components in the nuclear fusion environment, where the neutron irradiation damage is expected to cause embrittlement. In particular, the work focuses on two aspects: bending tests to deduce the onset of ductile deformation and microstructural analysis of the reference and plastically deformed materials. The microstructure in the reference state and the one induced by plastic deformation at 600 °C is studied by means of transmission electron microscopy (TEM). Six different types of tungsten-based materials were assessed: two commercial grades produced according to ITER specifications in Europe and China and four lab-scale grades utilizing different reinforcement options. The comparative assessment of tensile and bending strength was performed at 600 °C accompanied with a detailed TEM analysis. The deformation-induced microstructure was characterized and compared for all studied grades in terms of the dislocation density, heterogeneity, observation of pile-ups and tangles specifically near grain boundaries and/or strengthening particles. The obtained data will serve as reference information required to assess the impact of neutron irradiation.