(1. 兰州理工大学 省部共建有色金属先进加工与再利用国家重点实验室，兰州 730050； 2. 兰州理工大学 有色金属合金及加工教育部重点实验室，兰州 730050)
摘 要: 通过金属型铸造制备新型Mg-6Zn-3Al(ZA63，质量分数，%)镁合金，并利用光镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)和力学性能测试研究ZA63合金在铸态、固溶和时效处理后显微组织和力学性能的变化规律。结果表明：合金铸态组织主要由基体α-Mg、晶界处呈连续或半连续分布的(α-Mg+Mg2Zn3+Mg7Zn3+Mg32(Al,Zn)49)共晶和晶内孤立的颗粒相组成。合金在350 ℃固溶12~36 h时，随着时间延长，固溶效果逐渐增强，且在28 h时获得了较好的组织和241 MPa的抗拉强度及11.12%的伸长率。随后在180 ℃时效 6~72 h后，合金的抗拉强度进一步提高，力学性能随保温时间延长呈先增加后减小的趋势，其中时效24 h时同时出现抗拉强度、伸长率和硬度的峰值298 MPa、9.78%和96.3 HV，比铸态的214 MPa、8.54%、62.2 HV分别提高39.25%、14.52%和54.82%。180 ℃时效24 h后，析出相的主要形态有板条状和短棒状。
关键字: Mg-6Zn-3Al镁合金；固溶处理；时效处理；显微组织；力学性能；析出相形态
（1. State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China; 2. Key Laboratory of Non-ferrous Metal Alloys and Processing, Ministry of Education, Lanzhou University of Technology, Lanzhou 730050, China）
Abstract:A new type Mg-6Zn-3Al (noted ZA63, mass fraction, %) magnesium alloy was prepared by permanent mould casting, and the microstructure and mechanical properties of the alloy under the conditions of as-cast, solution and aging treatment were systematically investigated by OM, SEM, TEM, XRD and mechanical tests, respectively. The results indicate that the as-cast alloy is mainly comprised of matrix α-Mg, eutectic phases (α-Mg+Mg2Zn3+Mg7Zn3+ Mg32(Al,Zn)49) with continuous or semi-continuous precipitated along grain boundaries and a few divorced granules within grains. When the alloy is treated at 350 ℃ for 12-36 h, the solution effects are gradually enhanced with increasing solution time. At 350 ℃ for 28 h, the alloy reveals relatively homogeneous microstructure, and the ultimate tensile strength (UTS) and elongation (EL) of 241 MPa and 11.12% are achieved, respectively. Subsequently, when the alloy is aged at 180 ℃ for 6-72 h, the mechanical test demonstrates that, the UTS further increases, the mechanical properties increase firstly and then decrease, the peak values of UTS, EL and micro-hardness of the alloy aged at 180 ℃ for 24 h are simultaneously obtained, which are 298 MPa, 9.78% and 96.3 HV and increase by 39.25%, 14.52% and 54.82% compared with those of the as-cast alloy (214 MPa, 8.54% and 62.2 HV), respectively. There are mainly two types of precipitates of the alloy after aging at 180 ℃ for 24 h, namely, the first precipitate is lath-like, the secondary one is a short-rod.
Key words: Mg-6Zn-3Al magnesium alloy; solution treatment; aging treatment; microstructure; mechanical property; precipitation morphology
