Stacking disordered structures in Mg–Co–Y alloys

Abstract

Stacking disordered (SD) structures in Mg–Co–Y as-cast alloys have been examined using atomic-scale high-angle annular dark-field scanning transmission electron microscopy. All these SD structures mainly consist of F-blocks, T-blocks, 2-Mg, 3-Mg, and 4-Mg, which are the structural components of previously observed 15R, 12H, 21R, and 18R LPSO structures. These components can further form complex structures with similar stacking characters, which are disordered or locally ordered. The stacking sequence, periodicity, and symmetry of these SD structures were characterized and illustrated by our previously introduced notation. The structural similarity and difference between the SD structures and LPSO structures featuring various stacking layers were analyzed by comparing their stacking sequences, the arrangement of clusters in the basal plane and along the stacking directions.