Abnormal difference of hydrogen-induced ductility loss in nickel-based alloy 625 at conventional and slow strain rate.

Alloy 625 plays a crucial role in high-pressure hydrogen environments typical of hydrogen refuelling stations, where cyclic temperature and loading conditions prevail. In this study, we reveal that hydrogen-induced ductility loss of nickel-based alloy 625 significant difference which change from 11.9% at slow strain rate to 20.1% at conventional strain rate. The difference can be attributed to a change in deformation mode: from dislocation slipping under slow strain rate to twinning under conventional strain rate. Specifically, hydrogen-refined deformation twins and the promotion of twin bundles under conventional strain rates diminish the twin-induced plasticity effect of the alloy. This shift in deformation mode also alters the hydrogen embrittlement mechanism across the two strain rates. These findings provide valuable insights for hydrogen embrittlement-resistant designing and evaluating hydrogen compatibility for alloy 625. [Display omitted] • The nickel-based alloy 625 has more significant hydrogen-induced ductility loss at 5 × 10−3 s−1 than that at 5 × 10−6 s−1. • The deformation mode change from dislocation slipping at 5 × 10−6 s−1 to twinning at 5 × 10−3 s−1. • Hydrogen weakens the TWIP effect of the alloy because of hydrogen refining DTs. • Hydrogen will promote the formation of deformation twin bundles, resulting in cracking along DTs. • A new mechanism of hydrogen-induced cracking along DTs in nickel-based alloys was proposed. [ABSTRACT FROM AUTHOR]