Chemomechanical Origin of Hydrogen Trapping at Grain Boundaries in FCC Metals

TL;DR

This study uncovers the chemomechanical mechanisms behind hydrogen trapping at grain boundaries in FCC metals, providing a formula to predict hydrogen segregation energetics and aiding in designing embrittlement-resistant metals.

Contribution

It introduces a chemomechanical model linking atomic-scale interactions to hydrogen trapping at grain boundaries in FCC metals, advancing understanding and predictive capabilities.

Findings

Identified interstitial sites using polyhedral tessellation.

Established a chemomechanical formula for hydrogen segregation energetics.

Provided explanations for experimental hydrogen trapping observations.

Abstract

Hydrogen embrittlement of metals is widely observed, but its atomistic origins remain little understood and much debated. Combining a unique identification of interstitial sites through polyhedral tessellation and first-principles calculations, we study hydrogen adsorption at grain boundaries in a variety of face-centered cubic metals of Ni, Cu, gamma-Fe and Pd. We discover the chemomechanical origin of variation of adsorption energetics for interstitial hydrogen at grain boundaries. A general chemomechanical formula is established to provide accurate assessments of hydrogen trapping and segregation energetics at grain boundaries, and it also offers direct explanations for certain experimental observations. The present study deepens our mechanistic understanding of the role of grain boundaries in hydrogen embrittlement, and promises a viable path towards predictive microstructure engineering against hydrogen embrittlement in structural metals.