Atomistic study of grain-boundary segregation and grain-boundary diffusion in Al-Mg alloys

TL;DR

This study uses atomistic simulations to predict Mg segregation and diffusion in Al-Mg alloy grain boundaries, revealing how Mg impacts atomic mobility and microstructure stability.

Contribution

It provides the first computational predictions of Mg grain boundary segregation and diffusion in Al alloys, filling a gap in experimental data.

Findings

Mg segregates to tilt grain boundaries forming anisotropic clusters

Mg diffusion in Al grain boundaries is slower than Al diffusion

Mg segregation reduces mass transport along grain boundaries

Abstract

Mg grain boundary (GB) segregation and GB diffusion can impact the processing and properties of Al-Mg alloys. Yet, Mg GB diffusion in Al has not been measured experimentally or predicted by simulations. We apply atomistic computer simulations to predict the amount and the free energy of Mg GB segregation, and the impact of segregation on GB diffusion of both alloy components. At low temperatures, Mg atoms segregated to a tilt GB form clusters with highly anisotropic shapes. Mg diffuses in Al GBs slower than Al itself, and both components diffuse slowly in comparison with Al GB self-diffusion. Thus, Mg segregation significantly reduces the rate of mass transport along GBs in Al-Mg alloys. The reduced atomic mobility can be responsible for the improved stability of the microstructure at elevated temperatures.