Simulation of Early-stage Clustering in Ternary Metal Alloys Using the Phase Field Crystal Method

TL;DR

This paper applies phase field crystal methodology to simulate early-stage clustering in ternary Al alloys, revealing how Mg addition influences nucleation and cluster formation, consistent with experimental observations.

Contribution

It introduces the first application of phase field crystal method to ternary Al alloys, analyzing alloy composition effects on clustering behavior and nucleation mechanisms.

Findings

Mg increases nucleation rate by enhancing driving force and stress relaxation.

Small clusters show higher Mg affinity than larger Cu-rich clusters.

Two-stage clustering phenomenon is observed and explained.

Abstract

Phase field crystal methodology is applied, for the first time, to study the effect of alloy composition on the clustering behavior of a quenched/aged supersaturated ternary Al alloy system. An analysis of the work of formation is built upon the methodology developed in Fallah {\it et al.} to describe the dislocation-mediated formation mechanisms of early clusters in binary alloys [Phys. Rev. B., DOI: 10.1103/PhysRevB.00.004100]. Consistent with the experiments, we demonstrate that the addition of Mg to an Al-1.1Cu alloy increases the nucleation rate of clusters in the quenched/aged state by increasing the effective driving force for nucleation, enhancing the dislocation stress relaxation and decreasing the surface energy associated with the Cu-rich Cu-Mg co-clusters. Furthermore, we show that it is thermodynamically favourable for small sub-critical clusters to have higher affinity for Mg than larger overcritical Cu-rich clusters, particularly depicting a two-stage clustering phenomenon.