The formation mechanism of the lamellar phase precipitated during solid solution treatment in the Mg-Gd-Al alloy
Yongpeng Zhuang, Pengwen Zhou, Hongxia Wang, Kai-bo Nie, Yiming Liu, Wei Liang, Lifei Wang, Liuwei Zheng
Abstract
A large amount of lamellar phases were precipitated in Mg-9Gd-xAl (x = 0.4, 0.6, 0.8, 1.0, 3.0 wt.%) alloy after solution treatment. In order to explore the composition and formation condition of the lamellar phase, the Mg-9Gd-xAl alloys were subjected to solution treatment at different time, then the influence of lamellar phase on mechanical properties was investigated in Mg-9Gd-xAl alloys. The results indicate that the lamellar phase consists of three elements, Mg, Al, and Gd, and the atomic ratio is close to 1:1:1. It was identified that the lamellar phase is (Mg, Al)2Gd phase which has the same crystal structure with Al2Gd. In addition, the lamellar phases were parallel to each other inside one grain, but the alignment directions inside the adjacent grains were different, which provide strong second phase strengthening effect. After solution treatment, the ultimate tensile strength of Mg-9Gd-0.6Al alloy with abundant lamellar phase is greatly improved to 193 MPa.