A systematic investigation of secondary phase dissolution in Mg-Sn alloys

As-cast Mg-Sn alloys (3, 6, and 9 wt% Sn) were solution treated at 653, 703 and 753 K (380, 430 and 480 degrees C) for 1, 4, 8, 12 and 24 h to determine the variation of secondary phase with respect to Sn content, temperature and time. Mg-3 wt% Sn exhibits Mg2Sn dissolution at all solution treatment temperatures whereas Mg-6 and 9 wt% Sn alloy displays Mg2Sn reprecipitation and dissolution depending on the heat treatment temperature. In addition, a combined mathematical model that predicts the secondary phase dissolution and solute redistribution as a function of temperature and time is presented in this work. This model is a significant improvement compared to the previous studies where the dissolution and homogenization processes are considered independently. The effect of grain size and solute mobility upon the dissolution and homogenization kinetics is discussed as well. (C) 2019 Published by Elsevier B.V. on behalf of Chongqing University.