Solidification and microstructure of as-cast Mg₆₅Zn₃₂Y₃ quasicrystal alloy

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• 作者：Jiwei Geng ; Xinying Teng ; ^{mse_tengxy@ujn.edu.cn} ; Guorong Zhou ; Zhenwei Zhao
• 关键词：Mg&ndash ; Zn&ndash ; Y alloy ; Quasicrystal ; Resistivity ; Phase transformation
• 刊名：Physica B
• 出版年：2013
• 出版时间：1 July, 2013
• 年：2013
• 卷：420
• 期：Complete
• 页码：64-69
• 全文大小：1348 K

文摘

Stable icosahedral quasicrystal with a nominal composition of Mg₃₀Zn₆₀Y₁₀ (at % ) was prepared by an as-cast method. Applying X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, the equilibrium solidification microstructures of Mg₆₅Zn₃₂Y₃ (at % ) quasicrystal alloy in Mg-rich corner of the Mg-Zn-Y system was investigated. Since resistivity is one of the physical properties sensitive to structures, it is suggested that there is a reversible temperature-induced solid-liquid structural transition. Quasicrystal possesses quasi-periodic lattice structure and especial electronic structure, which indicates the resistivity of Mg₆₅Zn₃₂Y₃ quasicrystal alloy will change greatly during the melting or solidification processes. The temperature dependence on resistivity exhibits a clear turning point. Measuring resistivity-temperature curve (¦Ñ-T curve) and comparing with differential scanning calorimetry (DSC) first time, a study on the solidification process of quasicrystal was carried out. The icosahedral quasicrystalline phase (I-phase) surrounded by eutectic microstructure (¦Á-Mg+decagonal quasicrystalline phase (D-phase)) is reported first time. During the solidification process, the I-phase is formed at about 423 ¡ãC undergoing a peritectic reaction, and decagonal quasicrystal eutectic microstructure is formed at the later stage. The phase involved in this peritectic reaction has a composition of Mg_28.93Zn_46.62Y_24.35 (W-phase). Furthermore, the quasicrystals with various characteristics morphologies exist some degree micro-segregation. And the microsegregation phenomenon in rod-like quasicrystalline phase is more serious than that in petals-like quasicrystalline phase.