Direct Imaging of Hydrogen-Driven Dislocation and Strain Field Evolution in a Stainless Steel Grain

TL;DR

This study uses advanced X-ray imaging to observe how hydrogen affects dislocation movement and strain in stainless steel, providing experimental validation of theoretical models and insights for developing hydrogen embrittlement-resistant materials.

Contribution

It introduces in situ 3D imaging of hydrogen-driven dislocation dynamics in bulk steel, bridging the gap between simulations and experimental observations.

Findings

Hydrogen enhances dislocation mobility and relaxation.

Dislocation unpinning and climb are driven by osmotic forces.

Hydrogen induces elastic shielding around dislocations.

Abstract

Hydrogen embrittlement (HE) poses a significant challenge to the durability of materials used in hydrogen production and utilization. Disentangling the competing nanoscale mechanisms driving HE often relies on simulations and electron-transparent sample techniques, limiting experimental insights into hydrogen-induced dislocation behavior in bulk materials. This study employs in situ Bragg coherent X-ray diffraction imaging to track three-dimensional dislocation and strain field evolution during hydrogen charging in a bulk grain of austenitic 316 stainless steel. Tracking a single dislocation reveals hydrogen-enhanced mobility and relaxation, consistent with dislocation dynamics simulations. Subsequent observations reveal dislocation unpinning and climb processes, likely driven by osmotic forces. Additionally, nanoscale strain analysis around the dislocation core directly measures hydrogen-induced elastic shielding. These findings experimentally validate theoretical predictions and offer mechanistic insights into hydrogen-driven dislocation behavior. The quantified nanoscale phenomena serve as critical inputs for multiscale modeling frameworks to predict bulk material responses and accelerate the development of HE-resistant alloys.