Ab initio based analysis of grain boundary segregation in Al-Mg and Al-Zn binary alloys

TL;DR

This study uses ab initio simulations to analyze how Mg and Zn atoms interact with grain boundaries in aluminum alloys, revealing different segregation mechanisms and their dependence on element chemistry.

Contribution

It introduces a detailed ab initio analysis of segregation mechanisms for Mg and Zn in Al alloys, highlighting the role of electronic and deformation interactions.

Findings

Mg segregates in wide regions with agglomerations due to deformation interactions.

Zn prefers interstitial positions and forms thin layers via electronic bonding.

Element chemistry critically influences segregation morphology.

Abstract

Based on ab-initio simulations, we report on the nature of principally different mechanisms for interaction of Mg and Zn atoms with grain boundaries in Al alloys leading to different morphology of segregation. The Mg atoms segregate in relatively wide GB region with heterogeneous agglomerations due to the deformation mechanism of solute-GB interaction. In contrast, in the case of Zn atoms an electronic mechanism associated with the formation of directional bonding is dominating in the solute-GB interaction. As a result, for Zn atoms it is energetically beneficial to occupy interstitial positions at the very GB and to be arranged into thin layers along the GBs. The results obtained show the essential role of elements chemistry in segregation formation and explain the qualitative features in morphology of GB segregation observed in Al-Mg and Al-Zn alloys with ultrafine grains.