Thermally stable quasicrystalline phase in a superplastic Mg–Zn–Y–Zr alloy

A Mg-rich Mg–Zn–Y–Zr alloy sheet, which contains two different particles, icosahedral quasicrystalline phase (I-phase) and Zr-rich phase in the fine-grained α-Mg matrix, has been developed by thermomechanical processes. With an addition of zirconium in the ternary Mg–Zn–Y alloy, the I-phase/α-Mg eutectic temperature increases to 500 °C and the lattice constant of the I-phase slightly increases, leading to a more thermally stable eutectic structure. The fine-grained Mg–Zn–Y–Zr alloy shows large elongations to failure at the temperature above 400 °C, and no cavity is formed at the interface between the α-Mg and the I-phase during superplastic deformation.