Atomic scale investigation of a novel metastable structure in aged Mg-Nd alloys

Aged Mg-3.0 wt% Nd alloys were investigated by high angle annular dark-field scanning transmission electron microscopy. A hitherto unreported metastable phase designated beta(3) can always emerge at the endpoints of beta(1) particles. The crystal structure of beta(3) phase is determined to an orthorhombic lattice (space group Cmcm). With the {111}(beta 1), planes acting as the basal plane of growth, beta(3) phase has three types of variants, which are related by a 120 degrees rotation with respect to each other around the same [001](beta 3) axis. In addition, several peculiar morphologies and further evolution of beta(3) phase were also analyzed. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.