Stable icosahedral phase in Mg₄₄Zn₄₄Gd₁₂ alloy

王旭东，杜文博，王朝辉，刘轲，李淑波

School of Materials Science and Engineering,Beijing University of Technology

摘 要：The microstructure of the as-cast Mg 44 Zn 44 Gd 12 alloy was investigated by using X-ray diffraction（XRD）,differentical scanning（DSC）,scanning electron microscopy（SEM） and a detailed transmission electron microscope.The XRD,DSC and SEM results indicated that the as-cast Mg 44 Zn 44 Gd 12 alloy were mainly composed of three types of phases:the primary solidification phase,the dendritic phase and the eutectic phase.The primary solidification phase had an icosahedral structure.The dendritic phase was the W-phase,and eutectic structure phase was the Mg 7 Zn 3 phase.Microstructures of icosahedral phase（I-phase）,W-phase and Mg 7 Zn 3 phase in Mg 44 Zn 44 Gd 12 alloy were investigated.The results indicated that the I-phase in Mg 44 Zn 44 Gd 12 alloy was a face-centered icosahedral quasicrystal with stoichiometric composition of Mg 42 Zn 50 Gd 8 which had an excellent thermal stability up to 420 °C.The solid solution of the Gd gradually decreased during solidification,which played an important role in activating the formation of Mg 7 Zn 3 phase and W-phase from icosahedral phases.

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