Combining the K-bubble strengthening and Y-doping: Microstructure, mechanical/thermal properties, and thermal shock behavior of W-K-Y alloys

Nano‑potassium bubble strengthened tungsten (W-K) alloy with excellent overall performance has been proven to be one of the most desirable plasma facing materials (PFMs). However, some key properties, e.g., thermal heat resistance, ductile-brittle transition temperature (DBTT), strength and toughness need to be further improved to meet the requirements of fusion reactor. Herein, pure yttrium (Y) was doped in W-K alloy to achieve multiple strengthening effects. The grains of W-K alloy have been significantly refined, and the tensile strength was improved along with the introducing of Y. Thermal shock cracking threshold has increased to exceed 0.62 GW/m2. Interestingly, the existing form and size of the precipitates differed with the change of doping amount, leading to the nonlinear evolution of DBTT. The W-K alloy with 0.1 wt%-Y doping content (W-K-0.1Y) showed the best match of strength and toughness. Furthermore, coupled with relatively good thermal conductivity, W-K-0.1Y alloy displayed prominent thermal shock resistance. This work may pave a way for designing PFMs with higher performance.