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 formation, decohesion, and hydrogen-enhanced localized plasticity mechanisms. A more complete discussion of the failure mechanism based on hydrogen-enhanced dislocation mobility is presented, and these observations are related to measurements of the macroscopic now stress. The effects of hydrogen-induced slip localization on the measured now stress is discussed. A theory of hydrogen shielding of the interaction of dislocations with elastic stress centres is outlined. It is shown that this shielding effect can account for the observed hydrogen-enhanced dislocation mobility.