(1. 华南理工大学 材料科学与工程学院，广州 510640；2. 湖南大学 材料科学与工程学院，长沙 410082)
摘 要: 利用光学显微镜、显微硬度计、X射线衍射仪、扫描电镜和透射电镜分析时效热处理(T6)后的Mg-3Zn-1.5Cu-0.6Zr镁合金的析出相。结果表明：合金铸态组织主要由初晶Mg基体和非平衡共晶组织(Mg+Mg2Cu，CuMgZn)组成；经固溶处理，晶界处大部分非平衡共晶组织溶解。经180 ℃，16 h时效后，合金达到时效硬度峰值，此时晶内析出相主要有3类：1) 少量棒状的过渡相β1′-α(可能是Mg4Zn7)，其轴线垂直于(0001)Mg，长度大约50 nm；2) 大量弥散分布的板条状和棱柱状的β2′-MgZn2，其轴线垂直于(0001)Mg，长度为50~150 nm，该相是合金的主要时效硬化相；3) 少量短杆状的β-MgZn，其轴线平行于(0001)Mg，长度约20 nm。
关键字: 镁合金；Mg-Zn-Cu镁合金；MgZn2；MgZn；显微组织；时效硬化
as-cast Mg-3Zn-1.5Cu-0.6Zr Mg alloy
（1.School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China;
2.School of Materials Science and Engineering, Hunan University, Changsha 410082, China）
Abstract:The morphologies of the precipitates formed in an aged Mg-3Zn-1.5Cu-0.6Zr alloy were analyzed with optical microscope, microhardness tester, X-ray diffractometry(XRD), scanning electron microscope(SEM) and transmission electron microscope (TEM). The results show that the microstructure of the as-cast alloy is composed of the Mg matrix and nonequilibrium eutectic (Mg+Mg2Cu,CuMgZn) formed at the grain boundaries, and a majority of the nonequilibrium eutectics are dissolved after solution treatment. There are mainly three types of precipitates of alloy after aging at 180 ℃ for 16 h. The first one is a small amount of rod-like β1′-a(possibly Mg4Zn7), which has an average length of about 50 nm and is perpendicular to the base plane (0001)Mg of the Mg matrix. The second type of precipitate is a lath-like or prismatic β2′-MgZn2 with high-density and length of 50−150 nm, which is also perpendicular to the base plane of the Mg matrix and serves as the principal hardening phase of the aged alloy. The third precipitate is the short-rod like equilibrium β-MgZn, also in a small amount, with average length of about 20 nm and its axis is parallel to the base plane of the Mg matrix.
Key words: Mg alloy; Mg-Zn-Cu Mg alloy; MgZn2; MgZn; microstructure; age-hardening
