Comparative study on radiation resistance of WTaCrV high-entropy alloy and tungsten in helium-containing conditions

W and W-based high-entropy alloys are promising candidates for plasma-facing materials in fusion reactors. While irradiation studies on W have revealed a tendency for helium (He) bubble formation and radiation-induced defects, investigations of WTaCrV high-entropy alloy (HEA) have demonstrated superior radiation resistance, whether under He⁺ irradiation or heavy ion irradiation. To assess material performance under conditions relevant to fusion reactors-characterized by fast neutrons and gas production from transmutation reactions-complex irradiation environments need to be modeled. Using classical molecular dynamics simulations, we examined defect evolution in W and equimolar WTaCrV HEA with and without preexisting He atoms under overlapping displacement cascades up to 0.2 displacements per atom (dpa) at 300 K. In W, dislocation loops and large interstitial clusters formed readily, with increasing He content leading to higher dislocation densities and the formation of polygonal interstitial networks. In contrast, WTaCrV alloy exhibited strong resistance to formation of dislocation loops and large interstitial clusters but was more susceptible to bubble formation at higher He concentrations. Bubble growth was driven by helium trapping at vacancy sites and the coalescence of smaller bubbles. Larger bubbles remained stable against cascade overlap, limiting further growth by coalescence.