Mechanism of crack propagation due to hydrogen embrittlement in iron single crystals stressed along [001] axis

Striation-like hydrogen embrittlement (SHE) fracture occurs at low hydrogen concentration for an iron single crystal with a small carbon content, whil e cleavage fracture occurs at higher hydrogen concentration. The cleavage f racture initiated owing to hydrogen accumulated in front of the SHE crack t ip propagates extremely fast without plastic deformation. It is, however, u nder discussion whether a small amount of hydrogen causes lattice decohesio n or not.