Microstructure and phase composition of as-cast Mg-9Er-6Y-xZn-0.6Zr alloys
(1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;
2. National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China)
2. National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China)
Abstract: The microstructure and phase composition of as-cast Mg-9Er-6Y-xZn-0.6Zr (x=1, 2, 3, 4; normal mass fraction in %) alloys were investigated. In low Zn content, aside from the major second phase of Mg24(Er, Y, Zn)5, there are a few lamellar phases that grow parallel with each other from the grain boundaries to the grain interior. With Zn content increasing, the Mg24(Er,Y,Zn)5 phase decreases, but the Mg12Zn(Y, Er) phase and lamellar phases continuously increase. When Zn content reaches 4% (normal mass fraction), the Mg12Zn(Y,Er) phase mainly exists as large bulks, and some α-Mg grains are thoroughly penetrated by the lamellar phases. Moreover, the crystallography structures of the Mg12Zn(Y,Er) and Mg24(Er,Y,Zn)5 phases are confirmed as 18R-type long-period stacking ordered structure and body-centred cubic structure, respectively.
Key words: magnesium alloys; microstructure; phase composition; long-period stacking ordered (LPSO) structure phase