Abstract:The microstructure and mechanical properties of extruded Mg-Zn alloy containing Y element were investigated in temperature range of 300-450 °C and strain rate range of 0.001-1 s-1 through hot compression tests. Processing maps were used to indicate optimum conditions and instability zones for hot deformation of alloys. For Mg-Zn and Mg-Zn-Y alloys, peak stress, temperature and strain rate were related by hyperbolic sine function, and activation energies were obtained to be 177 and 236 kJ/mol, respectively. Flow curves showed that the addition of Y element led to increase in peak stress and decrease in peak strain, and indicated that DRX started at lower strains in Mg-Zn-Y alloy than in Mg-Zn alloy. The stability domains of Mg-Zn-Y alloy were indicated in two domains as 1) 300 °C, 0.001 s-1; 350 °C, 0.01-0.1 s-1 and 400 °C, 0.01 s-1 and 2) 450 °C, 0.01-0.1 s-1. Microstructural observations showed that DRX was the main restoration mechanism for alloys, and fully dynamic recrystallization of Mg-Zn-Y alloy was observed at 450 °C. The instability domain in Mg-Zn-Y alloy was located significantly at high strain rates. In addition, the instability zone width of Mg-Zn and Mg-Zn-Y alloys increased with increasing strain, and cracks, twins and severe deformation were considered in these regions.

Key words: Mg-Zn-Y alloy; I phase; processing map; microstructure; mechanical properties