Mitigating hydrogen embrittlement through microstructural shielding: Reverse-gradient design in high-entropy alloys

초록

High-strength alloys, commonly employed in industrial structural applications, often suffer from sudden fracture in hydrogen-containing environments. This is because the microstructure designed for strengthening is generally unfavorable for resisting hydrogen embrittlement, resulting in a trade-off dilemma between mechanical performance and hydrogen embrittlement resistance. To overcome this dilemma, in this work, we propose a new strategy for microstructural shielding against hydrogen embrittlement. The reverse-gradient structure, featuring a fully recrystallized surface region and a cold-rolled core region, was designed; thus, the surface region's high resistance to hydrogen embrittlement effectively shields the hydrogen-vulnerable core region. Further, the microstructural heterogeneity of the reverse-gradient layers induces high synergistic hardening, leading to an excellent combination of strength and ductility. The reverse-gradient sample exhibits a comparable ductility loss after hydrogen charging to that of its fully annealed counterparts, despite its much higher yield strength (2.4 times). This work proposes a promising process design for mitigating hydrogen embrittlement while showing excellent mechanical performance.

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