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 embrittlementresistant designing and evaluating hydrogen compatibility for alloy 625.