(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: 通过在Mg-6Zn合金中添加0.4%Zr和2%Sm(质量分数)制备出一种新型Mg-6Zn-2Sm-0.4Zr合金；利用光学显微镜(OM)、扫描电镜(SEM)及能谱仪(EDS)、X射线衍射仪(XRD)、显微硬度及力学性能测试研究铸造Mg-6Zn-2Sm-0.4Zr合金在铸态、固溶、时效处理下的显微组织和力学性能的变化。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+Mg41Sm5)共晶和晶内孤立的点状相组成。合金在440和450 ℃固溶12~36 h时间范围内，随着时间和温度的增加，固溶效果逐渐增强。当在450℃固溶28 h时获得了较好的显微组织，抗拉强度为230 MPa，伸长率为9.58%。随后经200 ℃时效6~48 h后，合金的力学性能明显提高，时效强化效应随时间的延长呈先增加后减小的趋势，其中时效12 h时同时出现了抗拉强度和伸长率的峰值258 MPa和14.43%，比铸态的分别提高44 MPa和90.80%。
关键字: Mg-6Zn-2Sm-0.4Zr镁合金；固溶处理；时效处理；显微组织；力学性能
（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-2Sm-0.4Zr alloy was fabricated by adding 0.4%Zr and 2%Sm (mass fraction) in Mg-6Zn alloy, and the microstructure and mechanical properties of the cast alloy under the conditions of as-cast, solution and aging treatment were investigated by optical microscopy (OM), scanning electron microscopy (SEM) with equipped energy dispersive spectrometry (EDS), X-ray diffractometry (XRD), micro-hardness and mechanical tests. The results indicate that the as-cast alloy is mainly composed of matrix α-Mg, eutectic phases (α-Mg+Mg2Zn3+Mg41Sm5) with continuous or semi-continuous morphology distributed along grain boundaries and a few isolated particles inside grains. The alloy is solutionized at 440 ℃ and 450 ℃ for 12-36 h, with the increment of solution temperature and time, the solution effect gradually increases. When the alloy is treated at 450 ℃ for 28 h, the alloy exhibits relatively homogeneous microstructure and attains mechanical performance with ultimate tensile strength (UTS) of 230 MPa and elongation (EL) of 9.58%, respectively. After the alloy being aged at 200 ℃ for 6-48 h, the mechanical properties of alloy increase obviously, and the aging strengthening effect increases firstly and then decreases, the peak values of UTS (258 MPa) and EL (14.43%) of the alloy aged at 200 ℃ for 12 h are simultaneously obtained, which are increased by 44 MPa and 90.80% compared with those of the as-cast alloy, respectively.
Key words: Mg-6Zn-2Sm-0.4Zr magnesium alloy; solution treatment; aging treatment; microstructure; mechanical property
