Chemical Short-Range Order Regulates Hydrogen Energetics and Hydrogen-Dislocation Interactions in CoNiV

TL;DR

This study uses machine learning to explore how chemical short-range order in CoNiV alloys influences hydrogen behavior and dislocation interactions, revealing that chemical ordering can reduce hydrogen uptake and alter dislocation dynamics.

Contribution

We develop a machine-learning interatomic potential to investigate the impact of chemical short-range order on hydrogen energetics and dislocation behavior in CoNiV alloys.

Findings

V-centered ordering suppresses V-V clustering.

Ordered alloys have higher hydrogen solution energies.

Hydrogen acts as a shallow, reversible trap at dislocation cores.

Abstract

Chemical short-range order (CSRO) has emerged as a critical structural feature in concentrated alloys, yet its coupling with hydrogen remains an active discussion. Here, we develop a machine-learning interatomic potential for the Co-Ni-V-H system and investigate how CSRO regulates hydrogen energetics and dislocation behavior in CoNiV, an alloy with reported strong resistance to hydrogen embrittlement. We identify strong V-centered ordering that suppresses V-V clustering and significantly reshapes the hydrogen solution landscape. Compared to a chemically random alloy, the ordered state exhibits higher average hydrogen solution energies and a reduced population of strongly binding sites, indicating lower bulk hydrogen uptake. At partial dislocations, hydrogen preferentially segregates to tensile core regions, acting as a shallow, reversible trap with a much weaker effect compared to chemical trapping states. These results demonstrate that local chemical order strongly regulates hydrogen-dislocation coupling and provide an atomistic understanding for tuning hydrogen-assisted deformation in concentrated CoNiV alloys.