Growth and morphology evolution of icosahedral quasicrystal phase in Mg ₃₀Zn ₆₀Y ₁₀ alloy

The formation process of the icosahedral quasicrystal phase (I-phase) in Mg ₃₀Zn ₆₀Y ₁₀ alloy and the different solidification microstructure formed under the different cooling rate have been investigated by using of the gravity chill-casting technique and SEM, XRD, DTA and TEM analysis. The results indicate that under a moderate cooling rate, the I-phase is formed by the peritectic reaction between a primary crystal phase and residual Mg-enriched melt. A transition from polygonal morphology to fine dendritic structure of the I-phase and primary phase selection will occur when a critical cooling rate is achieved. The peritectic reaction temperature, i.e., the formation temperature of the I-phase can be influenced by the cooling rate when DTA analysis is performed.