Hydrogen embrittlement controlled by reaction of dislocation with grain boundary in alpha-iron

TL;DR

This study uses atomistic modeling to reveal how hydrogen interactions with grain boundaries and dislocations in alpha-iron lead to embrittlement, providing insights into fracture mechanisms in polycrystalline metals.

Contribution

It demonstrates that dislocation-grain boundary reactions with hydrogen are key to understanding hydrogen embrittlement in polycrystalline alpha-iron, offering a new mechanistic perspective.

Findings

Dislocation impingement activates grain boundaries with disordered structures.

Hydrogen presence facilitates grain boundary decohesion.

The proposed model explains experimental observations of embrittlement.

Abstract

Hydrogen atoms absorbed by metals in the hydrogen-containing environments can lead to the premature fracture of the metal components used in load-bearing conditions. Since metals used in practice are mostly polycrystalline, grain boundaries (GBs) can play an important role in hydrogen embrittlement of metals. Here we show that the reaction of GB with lattice dislocations is a key component in hydrogen embrittlement mechanism for polycrystalline metals. We use atomistic modeling methods to investigate the mechanical response of GBs in alpha-iron with various hydrogen concentrations. Analysis indicates that dislocations impingement and emission on the GB cause the GB to locally transform into an activated state with a more disordered atomistic structure, and introduce a local stress concentration. The activation of the GB segregated with hydrogen atoms can greatly facilitate decohesion of the GB. We show that the hydrogen embrittlement model proposed here can give better explanation of many experimental observations.