Outstanding radiation resistance of tungsten-based high-entropy alloys

TLDR

The alloy was fabricated as thin films with a bimodal grain size distribution and a distinctive 4‑nm lamella‑like structure, and theoretical ab initio/Monte Carlo modeling predicts Cr‑ and V‑rich second‑phase particles and equal point‑defect mobilities as the basis for its radiation tolerance. The W‑based high‑entropy alloy exhibits exceptional radiation resistance, showing no dislocation loops after 8 dpa, maintaining a hardness of 14 GPa with negligible irradiation hardening, and developing Cr‑ and V‑rich second‑phase particles that correlate with black spots observed after thermal annealing.

Abstract

A body-centered cubic W-based refractory high entropy alloy with outstanding radiation resistance has been developed. The alloy was grown as thin films showing a bimodal grain size distribution in the nanocrystalline and ultrafine regimes and a unique 4-nm lamella-like structure revealed by atom probe tomography (APT). Transmission electron microscopy (TEM) and x-ray diffraction show certain black spots appearing after thermal annealing at elevated temperatures. TEM and APT analysis correlated the black spots with second-phase particles rich in Cr and V. No sign of irradiation-created dislocation loops, even after 8 dpa, was observed. Furthermore, nanomechanical testing shows a large hardness of 14 GPa in the as-deposited samples, with near negligible irradiation hardening. Theoretical modeling combining ab initio and Monte Carlo techniques predicts the formation of Cr- and V-rich second-phase particles and points at equal mobilities of point defects as the origin of the exceptional radiation tolerance.