Impact of Angular Deviation from Coincidence Site Lattice Grain Boundaries on Hydrogen Segregation and Diffusion in Alpha-iron

TL;DR

This study investigates how angular deviations from ideal sigma3 CSL grain boundaries in alpha-iron affect hydrogen diffusion and embrittlement, revealing that perfect boundaries resist decohesion and have higher hydrogen diffusivity.

Contribution

It provides new insights into the impact of angular deviations on hydrogen behavior at CSL grain boundaries in alpha-iron using molecular simulations.

Findings

Ideal sigma3 GBs resist decohesion below saturation

Hydrogen diffusivity is highest along ideal GBs

Angular deviations influence hydrogen embrittlement susceptibility

Abstract

Coincidence Site Lattice (CSL) grain boundaries (GBs) are believed to be low-energy, resistant to intergranular fracture, as well as to hydrogen embrittlement. Nevertheless, the behavior of CSL-GBs are generally confused with their angular deviations. In the current study, the effect of angular deviation from the perfect sigma3 (111) [1-10] GBs in Alpha-iron on the hydrogen diffusion and the susceptibility of the GB to hydrogen embrittlement is investigated through molecular static and dynamics simulations. By utilizing Rice-Wang model it is shown that the ideal GB shows the highest resistance to decohesion below the hydrogen saturation limit. Finally, the hydrogen diffusivity along the ideal GB is observed to be the highest.