Effect of Mn on the formation of Mg-based spherical icosahedral quasicrystal phase

Three-dimensional spherical icosahedral quasicrystalline phase (I-phase) has been obtained by introducing Mn into Mg–Zn–Y alloy under normal casting conditions. Due to the addition of Mn, Mg45Zn47Y5Mn3 primary I-phase,which is thermodynamically stable and homogeneously distributed, has been generated instead of decahedral quasicrystalline phase during the solidification process; morphology of primary I-phase in the solidification microstructure changed from petal-like one (60–80 μm) to spherical one (≤20 μm). When the Mn content reached 2 wt.%, volume fraction of Mg45Zn47Y5Mn3 spherical I-phase in as-cast Mg–Zn–Y–Mn master alloy was about 30–40%. Meanwhile, primary I-phase with highest spheroidization ratio and highest circular degree can be obtained; brittleness and hardness of as-cast Mg–Zn–Y–Mn master alloy reduced while density of as-cast Mg–Zn–Y–Mn master alloy increased. By analyzing spheroidization mechanism of Mg-based I-phase, spheroidization theory of Mg-based quasicrystals could be enriched a lot and a new way will be provided for the industrialization of Mg-based quasicrystals.