(东北大学 材料各向异性与织构教育部重点实验室，沈阳 110819)
摘 要: 采用合金法，利用X射线衍射、扫描电镜及能谱成分分析等手段测定Mg-Zn-Al合金350 ℃时的相平衡关系及其成分，建立富镁角350 ℃等温截面。结果表明：α-Mg固溶体与L、φ、γ三相保持相平衡关系，不存在以前普遍认为的τ与α-Mg的相平衡。获得350 ℃时φ相成分范围，即53.5%~57.2%Mg、17.7%~30.7%Zn和15.8%~27.7%Al(摩尔分数)。Zn和Al两种元素可以同时固溶于α-Mg相中。但Al的加入提高了Zn在α-Mg中的溶解度，当α-Mg和L相平衡时，溶解度最大可达3.9%，远大于Mg-Zn二元系的2.1%。而当α-Mg与γ相平衡时，Zn的加入降低Al在α-Mg中的溶解度，即由Mg-Al二元系的7.8%降至5.2%。Al在Mg-Zn二元金属间化合物中的固溶度较大，可达7.7%，从而使其热稳定性得到提高。
关键字: Mg-Zn-Al三元系；相平衡；平衡合金法；固溶度
（Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education,
Northeastern University, Shenyang 110819, China）
Abstract:The phase equilibria and their compositions in the Mg-rich corner of Mg-Zn-Al ternary system at 350℃ were determined through the equilibrated alloy method by X-ray diffractometry (XRD) and scanning electron microscopy (SEM) assisted with energy dispersive spectroscopy (EDS), and thus the isothermal section of the Mg-rich corner at 350 ℃ in the ternary system was constructed. There are three phases at this temperature in equilibrium with α-Mg solid solution, including the liquid, φ and γ phases, while not the τ ternary intermetallic compound as previously accepted. Moreover, the composition ranges of the φ intermetallic compound, i.e., 53.5%-57.2%Mg, 17.7%-30.7%Zn and 15.8%-27.7%Al (mole fraction), are also obtained. The zinc and aluminum are simultaneously soluble in the α-Mg phase. The solubility of Zn in the α-Mg phase increases due to the addition of Al, and the maximum solubility is 3.0%Zn, more than that of Mg-Zn binary system (2.1%Zn) when the α-Mg solid solution is in equilibrium with the liquid phase. However, the solubility of Al in the α-Mg phase decreases due to the addition of Zn when the α-Mg phase is in equilibrium with the γ intermetallic compound, i.e., the Al solubility is 7.8% in the Mg-Al binary system, decreasing to 5.2%. At the same time, the solubility of the Al in the Mg-Zn intermetallic compound is improved to 7.7%.
Key words: Mg-Zn-Al ternary system; phase equilibrium; equilibrated alloy method; solubility
