Reconciling ultrahigh strength and hydrogen embrittlement resistance via discontinuous L12 precipitation in a high-entropy alloy

Abstract

Achieving ultrahigh strength in advanced structural materials without compromising their resistance to hydrogen embrittlement (HE) remains a critical challenge. Here, we introduce a design strategy that exploits discontinuous L12 precipitation of strengthening particles also boosting HE resistance in a high-entropy alloy. The discontinuous reaction first produces serrated grain boundaries that induce crack deflection at multiple scales, effectively arresting intergranular crack propagation. The precipitates are ordered, coherent L12 nanorods with a high hydrogen trapping capability, as revealed by direct isotopically-labelled atom probe measurements and density functional theory calculations, significantly inhibiting hydrogen diffusion. This unique microstructural combination underpins a tensile strength of ∼1.7 GPa with a 33% superior HE resistance compared to a single-phase face-centered cubic reference alloy. Our strategy not only breaks the conventional trade-off between strength and HE, but also delivers higher gains in both tensile strength and HE resistance than conventional approaches, establishing discontinuous L12 precipitation as a versatile strategy for designing ultrahigh-strength HE-resistant alloys, with potential applications in hydrogen infrastructure and beyond.