Section 9.9 - Hydrogen Transport and Interaction with Material Deformation: Implications for Fracture

Abstract

This chapter presents two models: non-hydride-forming systems and hydride-forming systems. It discusses; the validity, background, description of the model, identification of model, and how to use this model. The non-hydride-forming systems applies to a variety of systems, such as fcc, bcc, hcp, pure metals, solid solutions, precipitation-strengthened systems, and intermetallics. It is used to calculate the local hydrogen concentration qualified by hydrostatic stress and trapping induced by plastic straining. Then by using information on whether the fracture is strain or stress-controlled, one can predict the location of the first microcracking event in a specimen. The hydride-forming system applies to systems that fail predominantly by hydride formation and cleavage. These are systems in which hydrides are either stable or can be stabilized by the application of a stress field. Examples are the IVb and Vb metals and their alloys, as well as a number of other metals such as Mg and A1. This hydride mechanism is supported by microscopic observations and thermodynamic calculations.