Hydrogen embrittlement behavior of a precipitation-strengthened Al0.35CoCrFeNi complex concentrated alloy

Abstract

Hydrogen embrittlement (HE) remains one of the principal challenges limiting the application of structural materials in hydrogen-based energy systems. This study investigates the hydrogen embrittlement behavior of a precipitation-strengthened Al 0.35 CoCrFeNi complex concentrated alloy (CCA). Following thermomechanical processing and solution annealing at 1320 °C for 30 min, precipitation annealing at 700 °C and 900 °C produced FCC + L1 2 + B2 (PA700) and FCC + B2 (PA900) microstructures, respectively. After electrochemical hydrogen charging at 70 °C for 72 h, TDS measurements revealed a higher hydrogen content in the PA700 sample than in PA900 (20 ± 7 and 8 ± 4 wt. ppm, respectively). The PA700 sample exhibits a significantly higher embrittlement factor EF = 67% compared to the PA900 alloy (EF = 12%). Hydrogen charging of the PA700 sample resulted in a pronounced reduction in tensile ductility from 25.0% to 8.1% and a decrease in ultimate tensile strength (UTS) from 915 to 775 MPa. In contrast, the PA900 sample showed only a moderate reduction in tensile properties, with elongation decreasing from 34.0% to 30.0% and UTS from 684 to 659 MPa. Fractographic analysis revealed predominantly intergranular cracking in the PA700 sample, whereas hydrogen-assisted damage in the PA900 sample was localized mainly at FCC(A1)/BCC(B2) interfaces. The higher hydrogen content measured for PA700 is associated with its precipitation-generated microstructure, which differs from PA900 in the type, size and distribution of secondary phases and in grain-boundary decoration. The results indicate that HE is governed not only by the total hydrogen content but by the microstructure generated during precipitation annealing, which controls hydrogen accommodation, interface characteristics, and local crack initiation.

The authors' abstract, as published at the source. Intermetallics, 2026 · DOI ↗