A 12R long-period stacking-ordered structure in a Mg-Ni-Y alloy

A hitherto unreported long-period stacking-ordered (LPSO) phase, designated 12R, was observed in a Mg80Ni5Y15 (at.%) alloy. Microstructure was investigated by electron diffraction and high-angle annular dark-field scanning transmission electron microscopy. Results show that the 12R has a trigonal lattice (a = b = 1.112 nm, c = 3.126 nm, alpha = beta = 90 degrees, and gamma = 120 degrees). Unit cell of the 12R is consisted of three ABCA-type building blocks and each building block contains dominant Ni6Y8-type building clusters. A sound structural model is proposed based on relative positions of Ni(6)y(8) clusters in neighboring building blocks. (C) 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.