52 Hydrogen-Enhanced Plasticity and Failure Revisited 2012

Through the use of the focused-ion beam lift-out technique, the salient microstructural features immediately underneath fracture surfaces are revealed. In this paper, the technique will be described and the new insight obtained from studies of underlying microstructure associated with hydrogen-induced “quasi-cleavage” fracture surface in a ferritic steel and a martensitic steel, intergranular failure in nickel, as well as fatigue striations in 316 stainless steel will be described. A striking commonality in the microstructure immediately beneath these surfaces is the extent of the development of the dislocation structure. It will be argued that it is the accelerated development of a complex microstructure and the concurrent redistribution of hydrogen that determines the conditions for these hydrogen-induced failures.