Hamidreza Abdolvand, University of Western Ontario

Title: Hydrogen Embrittlement in Metal Alloys: Microstructure-Informed Modeling and Experimentation

Abstract

Zirconium and titanium alloys are widely used across various industrial sectors. At the microstructure level, they have similar crystallographic properties, such as having hexagonal close-packed (HCP) or body-centered cubic (BCC) crystals. The mechanical properties of these crystals are elastically and plastically anisotropic, which leads to the development of local stress or strain hotspots in the alloys. When exposed to a hydrogen-rich environment, these hotspots affect hydrogen diffusion, hydride formation, and hydride fracture. This process ultimately results in the degradation of the alloys’ mechanical properties.

This presentation focuses on the development of multiscale numerical models that couple the effects of deformation with hydrogen diffusion and embrittlement. The primary implemented framework is the crystal plasticity finite element method, coupled with diffusion and damage subroutines to simulate the nonuniform distribution of hydrogen atoms, the effects of hydride precipitation, and the mechanisms of microcrack formation in hydrides. In situ deformation experiments in a scanning electron microscope are conducted to validate the model and to study how microstructure affects hydrogen embrittlement and the response of the alloy. The comparison between the numerical model and experiment provides insight into how hydrogen partitioning takes place between HCP and BCC phases. In addition, by examining various damage initiation criteria, it is shown that the combination of resolved shear stress and resolved shear strain on the dominant slip system drives crack initiation and controls the direction of hydrides microcracks.