On atomic structure of Guinier-Preston Zone in Mg-Zn-Gd alloy

TL;DR

This study reveals the atomic structure of Guinier-Preston zones in Mg-Zn-Gd alloy using advanced microscopy and calculations, showing a layered Gd-Zn configuration and correcting previous unstable models.

Contribution

The paper combines experimental microscopy with first-principles calculations to accurately determine the atomic structure of G.P. zones in Mg-Zn-Gd alloy, clarifying previous inconsistencies.

Findings

G.P. zone consists of three atomic layers parallel to (0001) plane.

Outer layers are enriched with Gd, middle layer with Zn.

Previous models are unstable and relax to the present structure.

Abstract

The atomic structure of Guinier-Preston (G.P.) zone in an Mg-Zn-Gd alloy has been determined by combining atomic resolution high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) and first-principles calculation. The G.P. Zone consists of three atomic layers paralleling to (0001) plane of Mg matrix, where two outer layers enrich with Gd while the middle layer enriches with Zn. Moreover, it is found that most of the structures reported previously are unstable and should converge to the present result after atomic relaxation, even though the atomic species and positions in the middle layer vary in those models.