Grain boundary segregation spectrum in basal-textured Mg alloys: From solute decoration to structural transition

TL;DR

This study uses atomistic simulations to explore grain boundary segregation in basal-textured Mg alloys, revealing a bimodal segregation spectrum and structural transitions that influence alloy ductility and phase formation.

Contribution

It introduces a detailed atomistic analysis of segregation behavior and structural transitions in basal-textured Mg alloys, highlighting new segregation patterns and phase evolution insights.

Findings

Discovered a bimodal segregation energy distribution in basal-textured Mg alloys.

Identified grain boundary structural transitions influenced by thermodynamic variables.

Provided insights into phase formation relevant to alloy ductility improvements.

Abstract

Mg alloys are promising lightweight structural materials due to their low density and excellent mechanical properties. However, their limited formability and ductility necessitate improvements in these properties, specifically through texture modification via grain boundary segregation. While significant efforts have been made, the segregation behavior in Mg polycrystals, particularly with basal texture, remains largely unexplored. In this study, we performed atomistic simulations to investigate grain boundary segregation in dilute and concentrated solid solution Mg-Al alloys. We computed the segregation energy spectrum of basal-textured Mg polycrystals, highlighting the contribution from specific grain boundary sites, such as junctions, and identified a newly discovered bimodal distribution which is distinct compared to the conventional skew-normal distribution found in randomly-oriented polycrystals. Using a hybrid molecular dynamics/Monte Carlo approach, we simulated segregation behavior at finite temperatures, identifying grain boundary structural transitions, particularly the varied fraction and morphology of topologically close-packed grain boundary phases when changing thermodynamic variables. The outcomes of this study offer crucial insights into basal-textured grain boundary segregation and phase formation, which can be extended to other relevant Mg alloys containing topologically close-packed intermetallics.