Solidification of Mg-Zn-Y Alloys at 6 GPa Pressure: Nanostructure, Phases Formed, and Their Stability

摘要

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 alpha-Mg, Mg7Zn3, and Mg3YZn6, while Mg-6Zn-3Y consisted of alpha-Mg, Mg3Y2Zn3, and Mg3YZn6. After solidification at 6 GPa pressure, both alloys consisted of alpha-Mg, MgZn, and Mg12YZn. The size and the shape of the second-phase particles formed for atmospheric solidification were significantly different to those formed for solidification at 6 GPa pressure. In Mg-6Zn-1Y, the second-phase size decreased from 300 to 50 nm, and the shape changed from needle like to blocky. In Mg-6Zn-3Y, the size decreased from 100 to 50 nm and the shape changed from short rod like to small and round. After aging at 200 A degrees C for 12 h, the new MgZn phase transformed into the intermediate MgZn2 phase. Increasing the aging time to 24 h caused the intermediate MgZn2 phase to transform into Mg7Zn3 with a size of 50 nm, while the Mg12YZn phase remained unchanged.