Understanding the Influence of Hydrogen on BCC Iron Grain Boundaries using the Kinetic Activation Relaxation technique (k-ART)

TL;DR

This study investigates how hydrogen affects grain boundary behavior in BCC iron using the k-ART simulation method, revealing how hydrogen influences diffusion, stabilization, and energy landscapes at the atomic level.

Contribution

It provides novel insights into hydrogen's impact on grain boundary stability and diffusion mechanisms in BCC iron through advanced kinetic Monte Carlo simulations.

Findings

Hydrogen diffuses more slowly at grain boundaries than in the bulk.

Hydrogen saturation stabilizes grain boundaries by increasing diffusion barriers.

Hydrogen presence smooths the energy landscape, reducing diffusion events.

Abstract

Hydrogen embrittlement (HE) poses a significant challenge in the mechanical integrity of iron and its alloys. This study explores the influence of hydrogen atoms on two distinct grain boundaries (GBs), $\Sigma37$ and $\Sigma3$, in body-centered-cubic (BCC) iron. Using the kinetic activation-relaxation technique (k-ART), an off-lattice kinetic Monte Carlo approach, we examine diffusion barriers and mechanisms associated with these GBs. Our findings reveal distinct behaviors of hydrogen in different GB environments, emphasizing the elastic deformation that arises around the GB in the presence of H that leads to either the predominance of new pathways and diffusion routes or a pinning effect of H atoms. We find that, for these systems, while GB is energetically favorable for H, this element diffuses more slowly at the GBs than in the bulk. Moreover, with detailed information about the evolution landscape around GB, we find that the saturation of a GB with hydrogen both stabilizes the GB by shifting barriers associated with Fe diffusion to higher energies and smooths the energy landscape, reducing the number of diffusion events. This comprehensive analysis enhances our understanding of hydrogen's role in GB behavior, contributing valuable insights for the design and optimization of materials in hydrogen-related applications.