H induced decohesion of an Al grain boundary investigated with first principles: Proposed general conditions for instant breakage and delayed fracture

TL;DR

This study uses first principles to analyze how hydrogen affects the fracture behavior of an aluminum grain boundary, proposing conditions for instant breakage versus delayed fracture based on loading and hydrogen interactions.

Contribution

It introduces a model extending standard frameworks to include loading-unloading hysteresis and identifies conditions for delayed versus immediate fracture due to hydrogen influence.

Findings

Hydrogen tends to relocate during loading, affecting fracture behavior.

Delayed fracture occurs when hydrogen attraction decreases with increased loading.

Destabilization can be triggered by exceeding certain stress thresholds before maximum strain.

Abstract

The uniaxial tensile test response of a H decorated $\Sigma$ 5 [100] twist grain boundary (GB) in face-centered-cubic Al has been examined with first principles. The impurity shows a strong tendency to relocate during loading. To capture these H movements, the standard model framework was extended to probe loading-unloading hysteresis. If the maximum tensile stress accepted by the H decorated GB in the slow fracture limit is reached before the maximum acceptable strain, exceeding this stress may trigger a H influx-controlled destabilization, as opposed to 'immediate' breakage. Such 'delayed' failure appears likely whenever the H attraction to a GB displays a monotonic decrease with increased loading.