(東北大學(xué) 材料各向異性與織構(gòu)教育部重點實驗室，沈陽 110819)
摘 要: 采用合金法，利用X射線衍射、掃描電鏡及能譜成分分析等手段測定Mg-Zn-Al合金350 ℃時的相平衡關(guān)系及其成分，建立富鎂角350 ℃等溫截面。結(jié)果表明：α-Mg固溶體與L、φ、γ三相保持相平衡關(guān)系，不存在以前普遍認(rèn)為的τ與α-Mg的相平衡。獲得350 ℃時φ相成分范圍，即53.5%~57.2%Mg、17.7%~30.7%Zn和15.8%~27.7%Al(摩爾分?jǐn)?shù))。Zn和Al兩種元素可以同時固溶于α-Mg相中。但Al的加入提高了Zn在α-Mg中的溶解度，當(dāng)α-Mg和L相平衡時，溶解度最大可達3.9%，遠大于Mg-Zn二元系的2.1%。而當(dāng)α-Mg與γ相平衡時，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二元金屬間化合物中的固溶度較大，可達7.7%，從而使其熱穩(wěn)定性得到提高。
關(guān)鍵字: 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
