Formation of 14H long period stacking ordered structure and profuse stacking faults in Mg-Zn-Gd alloys during isothermal aging at high temperature

This paper proposes a time-temperature-transformation diagram of an Mg-Zn-Gd alloy. An Mg97Zn1Gd2 (at.%) alloy shows different precipitation sequences at low, medium and high temperatures. Low-temperature aging at < 523 K brings about coherent beta'-phase precipitation to a alpha-Mg solid solution, resulting in increase in strength of the alloys. However, aging at medium and high temperatures > 623 K led to strengthening of the Mg-Zn-Gd alloy, owing to the formation of profuse stacking faults and 14H long period stacking ordered structure from the supersaturated a-Mg matrix, respectively. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.