Thermodynamic competition and hydrogen redistribution by coherent nanoprecipitates in high-strength steels

Abstract

Abstract Designing nanoprecipitates as static hydrogen traps is a widely used strategy to mitigate hydrogen embrittlement (HE) in high-strength steels, yet increasing trapping capacity alone may not ensure resistance under dynamic loading. Here, the effect of Cu-rich precipitate evolution (B2 → BCC/9 R → FCC) on HE in low-alloy steels containing 0.2–1.7 wt.% Cu was systematically investigated. The 1.0Cu steel exhibited the lowest hydrogen embrittlement index ( I HE = 1.4%) and the best ductility retention. Density functional theory calculations combined with transmission electron microscopy showed that coherent/semi-coherent BCC/9R Cu-rich precipitate interfaces have a low hydrogen solution energy (−0.202 eV), making them thermodynamically favorable hydrogen-trapping sites. These interfaces may competitively trap hydrogen relative to dislocation-associated sites during deformation, thereby promoting hydrogen redistribution and reducing dislocation-mediated hydrogen transport and HELP-related localized plasticity. In contrast, the 1.7Cu steel, despite its higher apparent hydrogen concentration (1.4 × 10 −6 mol/cm 3 ), contains coarser FCC-related precipitates that introduce local stress concentrations and promote detrimental hydrogen accumulation. These results suggest that hydrogen-resistant alloy design should focus not simply on maximizing static trapping capacity, but on regulating precipitate structure and interfacial state to enable more effective dynamic hydrogen management.

The authors' abstract, as published at the source. npj Materials Degradation, 2026 · DOI ↗