Effects of heat treatment routes on microstructure and damping properties of Mg–Zn–Y–Mn alloys

The effects of different heat treatment processes on the morphology and damping properties of long-period stacking order (LPSO) phase in Mg-4.9Zn-8.9Y-xMn alloys were studied. The microstructure analysis shows that the as-cast second phase presents a vein-shaped distribution at the grain boundary, and the heat treatment temperature has a significant effect on the morphology of the second phase. After heat treatment at 540 °C, the LPSO phase at the grain boundary changes into rod-like; When the heat treatment temperature is 550 °C, the LPSO phase changes into bulk or flocculent, and part of the LPSO phase melts into the matrix.In this process, the addition of Mn also has an important influence on the morphology transformation of LPSO phase. An appropriate amount of Mn can divide the bulk LPSO into several small parts during heat treatment, thus forming a large number of dispersed LPSO phases. In general, heat treatment and Mn elements can affect the mechanical and damping properties of the alloy. Heat treatment can reduce the mechanical properties of the alloy, but effectively improve the damping properti es of the alloy. With the addition of Mn into the alloy, the mechanical properties of the alloy can be improved without significantly reducing the damping.