Effects of Zn / Y ratio on microstructure and mechanical properties of Mg-Zn-Y alloys

Microstructures and mechanical properties of Mg-Zn-Y alloys containing icosahedral phase (I-phase) as a secondary solidification phase have been investigated in the composition range where the total solute content (Zn and Y) is less than 10 wt.%. The optimum Zn / Y ratio for the formation of two-phase microstructure consisting of α-Mg and I-phase is 5∼7. The strength increases with increasing total solute content (Zn and Y), i.e. with increasing volume fraction of I-phase. In particular, the alloys containing I-phase exhibit high elongation to failure, > 25%, which is ascribed to the low interfacial energy between the I-phase particle and surrounding α-Mg crystalline matrix.