Tungsten–tantalum alloys for fusion reactor applications

Tungsten–tantalum (W-Ta) alloys containing 1–5%Ta were developed for fusion reactor applications. For the mechanical properties and resistance against recrystallization in the non-irradiated state, Ta-alloying improved the performance of W. Grain refining and solute Ta improved the recrystallization temperature and strength. In addition, W-1%Ta exhibited a superior ductility, including ductile-to-brittle transition temperature (DBTT), which might be attributed to the strength of sub-grain boundary. Proton irradiation study at 1500 °C to 0.5 dpa revealed a decrease in irradiation hardening (increase in hardness) in recrystallized specimens and a decrease in hardness reduction in as-received specimens with increasing Ta concentration. With respect to the high temperature irradiation of the as-received specimens, microstructural recovery followed by recrystallization could be one of the dominant factors affecting the hardness change. As a material performance required for the actual components of fusion reactors, resistance against high heat flux exposure have been studied through thermal shock tests. Thorough this experiment, it was clarified that the degradation by high heat flux exposure could be suppressed due to Ta-alloying.