High Radiation Resistance in the Binary W-Ta System Through Small V Additions: A New Paradigm for Nuclear Fusion Materials.

Refractory High-Entropy Alloys (RHEAs) are promising candidates for structural materials in nuclear fusion reactors, where W-based alloys are currently leading. Fusion materials must withstand extreme conditions, including i) severe radiation damage from energetic neutrons, ii) embrittlement due to H and He ion implantation, and iii) exposure to high temperatures and thermal gradients. Recent RHEAs, such as WTaCrV and WTaCrVHf, have shown superior radiation tolerance and microstructural stability compared to pure W, but their multi-element compositions complicate bulk fabrication and limit practical use. In this study, it is demonstrated that reducing alloying elements in RHEAs is feasible without compromising radiation tolerance. Herein, two Highly Concentrated Refractory Alloys (HCRAs) - WTaV and WTaV (at.%) - were synthesized and investigated. We found that small V additions significantly influence the radiation response of the binary W-Ta system. Experimental results, supported by ab-initio Monte Carlo simulations and machine-learning-driven molecular dynamics, reveal that minor variations in V content enhance Ta-V chemical short-range order (CSRO), improving radiation resistance in the WTaV HCRA. By focusing on reducing chemical complexity and the number of alloying elements, the conventional high-entropy alloy paradigm is challenged, suggesting a new approach to designing simplified multi-component alloys with refractory properties for thermonuclear fusion applications.