Hydrogen irradiation behavior of the CoCrFeMnNi high-entropy alloy

Abstract The microstructural evolution and irradiation-hardening behavior of a CoCrFeMnNi high-entropy alloy (HEA) were investigated under room-temperature H 2 -ion irradiation. After irradiation, a stable single-phase face-centered cubic structure was retained, and no evidence of phase decomposition was detected. Transmission electron microscopy revealed a nanoscale H-bubble layer in the damage-peak region, with a visible bubble-layer thickness of ∼430 nm and an average bubble size of 1.6 ± 0.3 nm. Irradiation-induced defects varied markedly with depth: in the front and damage tail regions, the dominant defects were high-density, fine 1/3〈111〉 Frank loops; in the damage-peak region, the loops increased in size while their number density decreased. Notably, a narrow ‘depletion band’ of 1/3〈111〉 Frank loops was observed at the center of the damage-peak region, suggesting that H incorporation may alter the nucleation and evolution of such loops in this HEA. Nanoindentation measurements indicated pronounced irradiation hardening, with a hardening increment of ∼60%, which was primarily attributed to strong pinning of dislocation glide by high-density Frank partial loops and H bubbles.