A new insight into the beta′′′ structure: Three categories of configurations between beta′ precipitates in aged binary Mg-Nd alloy

The morphology and the structure of βF′ metastable phase were studied in aged binary MgNd alloy by atomic-resolution scanning transmission electron microscopy (STEM). The proposed three categories of βF′ − βF′ configurations are respectively aligned, staggered and inserted configurations, which can explain well the β′′′ structure proposed previously based on the experimental images and constructed models. The inserted βF′ − βF′ configuration is the most important one during the structural evolution of aging, which play a crucial role in the in-situ transformation from the D019-like to the quasi-β1 structures.