On the micromechanism of hydrogen-assisted cracking in a single-crystalline iron–silicon alloy thin sheet

A microscopic analysis of sub-critical hydrogen-assisted cracking (HAC) in a single-crystalline iron–silicon thin sheet was conducted and revealed the following points: (i) crack tip geometry and crack growth unit (striation spacing) are constant even when crack length (i.e. apparent stress intensity) and crack velocity (da/dt) significantly change; and (ii) da/dt monotonically increases with plastic zone size. These findings suggest that the effect of large-scale plasticity on the rate-limiting process should be explicitly considered in the kinetic modeling of the HAC mechanism.