Solute-Driven Defect Engineering in a Tungsten‑Based High‑Entropy Alloy for Extreme Radiation Tolerance

Fusion energy demands materials that withstand extreme helium irradiation, a challenge that conventional tungsten fails to meet due to bubble embrittlement and hardening. Here we report a WTaVCr high-entropy alloy (HEA) in which chemical disorder fundamentally alters helium‑defect dynamics. Through ion irradiation, atomic‑scale microscopy, and atomistic simulations, we uncover a unique solute‑defect interplay that suppresses degradation. Unlike pure tungsten, the HEA retains nanometer‑scale helium bubbles (∼1 nm) without coarsening as the He fluence increases. Dislocation loops in the alloy showing an increasing fraction of < 100>‑type loops accompanied by Cr enrichment and Ta depletion at loop interfaces. Atomic-scale analysis and simulations unveil a thermodynamically driven segregation process where Cr enriches at dislocation loops while Ta is excluded, a direct result of atomic size mismatch and strain minimization. Nanoindentation reveals quantifiable hardening governed by loop density and character. These results demonstrate that configurational entropy alone is insufficient; deliberate solute‑dislocation interactions are critical for defect control. By linking chemical heterogeneity to microstructural evolution, this work provides a design principle for alloys that maintain mechanical integrity in high‑radiation environments, paving the way for durable fusion materials.