Microstructures and formation of quasicrystal phase in as-cast Mg₆₈Zn₂₉Y₃ alloy cooling with step die

Mg₆₈Zn₂₉Y₃ alloy with stable icosahedral quasicrystals were prepared by cast method cooling with a metal step die. The microstructures, composition and phases of the Mg₆₈Zn₂₉Y₃ alloy were analyzed by SEM and EDS. And the icosahedral quasicrystalline structure was identified by TEM. Results showed that the morphology, amount, distribution and grain size of I-phases were influenced by the cooling rate. The typical microstructures of I-phases were petal shaped, pentagon and hexagon. With cooling rate decreasing, I-phases changed from dispersion and fine to fragmentation and coarse, and the grain size grew up from 20 to 100 μm gradually, until crushing to block quasicrystal. The microstructures of the alloy consisted of MgZn+α-Mg+Zn₆₀Mg₃₀Y₁₀ (I-phase).