High temperature He bubble evolution and thermal stability of the WTaCrV refractory concentrated solid solution alloy

In this study, we investigate the thermal stability and high-temperature evolution of He bubbles within the structure of the WTaCrV refractory concentrated solid solution alloy (RCSA), which is dedicated to nuclear fusion applications. The material was first irradiated with He+ ions to form nanometric He bubbles within its structure. Subsequently, their high-temperature evolution was studied using an in-situ heating method in a transmission electron microscope over a temperature range of 700°C to 1000°C. We found that the bubbles are stable in size up to a temperature of 700°C and show no agglomeration up to 800°C. At higher temperatures, the coarsening of the bubbles occurs through the migration and coalescence mechanism; however, even at 1000°C, the size of the bubbles only slightly exceeds 1 nm. For a more in-depth understanding of the phenomena occurring during high-temperature annealing, molecular dynamics simulations were applied. We demonstrate that the low diffusivity of VmHen clusters in the investigated WTaCrV alloy is responsible for the low tendency for high-temperature coarsening of the bubbles. The results of this study highlight the potential of the WTaCrV RCSA as a refractory, irradiation-resistant material for crucial components in future fusion reactors.