HYDROGEN-ENHANCED LOCALIZED PLASTICITY - A MECHANISM FOR HYDROGEN-RELATED FRACTURE

The mechanisms of hydrogen-related fracture are briefly reviewed and a few evaluative statements are made about the stress-induced hydride f ormation, decohesion, and hydrogen-enhanced localized plasticity mecha nisms. A more complete discussion of the failure mechanism based on hy drogen-enhanced dislocation mobility is presented, and these observati ons are related to measurements of the macroscopic now stress. The eff ects of hydrogen-induced slip localization on the measured now stress is discussed. A theory of hydrogen shielding of the interaction of dis locations with elastic stress centres is outlined. It is shown that th is shielding effect can account for the observed hydrogen-enhanced dis location mobility.