Atomic-scale pathway of early-stage precipitation in Al-Mg-Si alloys

TL;DR

This study uncovers the atomic-scale pathway of early-stage precipitation in Al-Mg-Si alloys, revealing how solute clusters evolve and form precipitates, which is crucial for improving alloy strength.

Contribution

It provides the first detailed atomic-scale analysis of early-stage precipitation pathways in Al-Mg-Si alloys, including cluster evolution and dislocation association.

Findings

Identified a three-variant FCC clustering pathway leading to GP-zones.

Observed morphological evolution from spherical to elongated clusters.

Linked dislocation interactions with clustering phenomena.

Abstract

Strengthening in age-hardenable alloys is mainly achieved through nano-scale precipitates whose formation paths from the atomic-scale, solute-enriched entities are rarely analyzed and understood in a directly-verifiable way. Here, we discover a pathway for the earliest-stage precipitation in Al-Mg-Si alloys: solute clustering leading to three successive variants of FCC clusters, followed by the formation of non-FCC $GP$-$zones$. The clusters, which originally assume a spherical morphology ($C1$), evolve into elongated clusters and orient themselves on $\{111\}_{Al}$ ($C2$) and subsequently on $\{100\}_{Al}$ planes and $<$$100$$>_{Al}$ directions ($C3$). We also analyze the association of quenched-in dislocations with clustering phenomena. The results of this work can open a new frontier in advancing alloy-process-property design for commercially-important age-hardenable Al alloys.