The effect of grain boundary misorientation on hydrogen flux using a phase-field based diffusion and trapping model

TL;DR

This study uses a phase-field based mesoscale model to analyze how grain boundary misorientation affects hydrogen diffusion and trapping, revealing complex behaviors influenced by grain size, boundary type, and network connectivity.

Contribution

It introduces a fully kinetic mesoscale model to investigate hydrogen interactions at grain boundaries considering misorientation effects, advancing understanding of hydrogen embrittlement mechanisms.

Findings

Higher hydrogen content with smaller grain size due to increased GB density.

HAGBs exhibit higher hydrogen flux owing to greater enrichment and trap-binding energy.

Decreasing grain size increases breakthrough time and steady-state flux.

Abstract

Understanding hydrogen-grain boundary (GB) interactions is critical to the analysis of hydrogen embrittlement in metals. This work presents a mesoscale fully kinetic model to investigate the effect of GB misorientation on hydrogen diffusion and trapping using phase-field based representative volume elements (RVEs). The flux equation consists of three terms: a diffusive term and two terms for high and low angle grain boundary (H/LAGB) trapping. Uptake simulations showed that decreasing the grain size resulted in higher hydrogen content due to increasing the GB density. Permeation simulations showed that GBs are high flux paths due to their higher enrichment with hydrogen. Since HAGBs have higher enrichment than LAGBs, due to their higher trap-binding energy, they generally have the highest hydrogen flux. Nevertheless, the flux shows a convoluted behavior as it depends on the local concentration, alignment of GB with external concentration gradient as well as the GB network connectivity. Finally, decreasing the grain size resulted in a larger break-through time and a larger steady-state exit flux.