Solidification of Mg-Zn-Y alloys at 6\ua0GPa pressure: nanostructure, phases formed, and their stability

Mg-Zn-Y alloys solidified under high pressure were characterized using XRD, DTA, SEM, and TEM. After solidification at atmospheric pressure, Mg-6Zn-1Y consisted of α-Mg, MgZn, and MgYZn, while Mg-6Zn-3Y consisted of α-Mg, MgYZn, and MgYZn. After solidification at 6\ua0GPa pressure, both alloys consisted of α-Mg, MgZn, and MgYZn. The size and the shape of the second-phase particles formed for atmospheric solidification were significantly different to those formed for solidification at 6\ua0GPa pressure. In Mg-6Zn-1Y, the second-phase size decreased from 300 to 50\ua0nm, and the shape changed from needle like to blocky. In Mg-6Zn-3Y, the size decreased from 100 to 50\ua0nm and the shape changed from short rod like to small and round. After aging at 200\ua0°C for 12\ua0h, the new MgZn phase transformed into the intermediate MgZn phase. Increasing the aging time to 24\ua0h caused the intermediate MgZn phase to transform into MgZn with a size of 50\ua0nm, while the MgYZn phase remained unchanged