Akihide Nagao

Hydrogen Embrittlement Understood

The connection between hydrogen-enhanced plasticity and the hydrogen-induced fracture mechanism and pathway is established through examination of the evolved microstructural state immediately beneath fracture surfaces including voids, “quasi-cleavage,” and intergranular surfaces. This leads to a new understanding of hydrogen embrittlement in which hydrogen-enhanced plasticity processes accelerate the evolution of the microstructure, which establishes not only local high concentrations of hydrogen but also a local stress state. Together, these factors establish the fracture mechanism and pathway.

Recent advances on hydrogen embrittlement of structural materials

This paper presents a critical review of current understanding of the effect of hydrogen on fracture and fatigue of metals and alloys. First, microstructures found immediately beneath hydrogen-induced fracture surfaces in various materials are presented. Then, recent progress toward the fundamentals of hydrogen-induced fracture is reported. Lastly, a recent attempt to model hydrogen embrittlement by linking the macroscale (e.g. applied load and hydrogen content) and the operating microscopic degradation mechanism at the local microstructural defect level is reviewed.