Domain structures and the transitional state of ordering in long-period stacking ordered (LPSO) structures in Mg-Al-Gd alloy

TL;DR

This paper investigates the transitional ordering states in LPSO structures of Mg-Al-Gd alloys, revealing domain origins and cluster patterns, and explaining the growth process leading to the final ordered structure.

Contribution

It introduces a domain-based explanation for transitional states and cluster patterns in LPSO structures, enhancing understanding of their formation in Mg-Al-Gd alloys.

Findings

Domains are the origin of transitional states.

Three new cluster patterns are explained by superimposed L12 clusters.

Growth of preferred domains leads to final ordered LPSO structure.

Abstract

The transitional state of ordering in the long-period stacking ordered (LPSO) structure in Mg-Al-Gd alloy has been investigated by scanning transmission electron microscopy. It is found that the domains are the origin of observed transitional state. Three new patterns of clusters at this state can be fully explained by the superimposition of L12 type clusters located in different domains. The domains are further verified by different tilted views. Growth of preferred domains during ageing process will result in final ordered LPSO structure. Based on the idea of domains, less ordered LPSO structure in other dilute alloys can be also understood.