(1. 湖南大学 汽车车身先进设计制造国家重点实验室，长沙 410082；
2. 湖南大学 材料科学与工程学院，长沙 410082)
摘 要: 采用光学显微镜、扫描电子显微镜和X射线衍射仪等研究Sr对AZ91镁合金组织及力学性能的影响。结果表明：添加微量Sr可以细化并离散AZ91合金的铸态共晶组织，在合金晶界处Sr与Al生成多角块状或杆状的Al4Sr高熔点相；当Sr含量为0.2%时，AZ91-0.2Sr合金的综合力学性能最优，AZ91-Sr合金的时效进程与AZ91合金相比明显被抑制。由于这些析出相及合金晶界附近Al4Sr高熔点相的强化作用，AZ91-0.2Sr合金经T6处理后的室温和高温力学性能皆优于原AZ91合金的。
关键字: AZ91镁合金；锶；合金化；T6处理；显微组织；力学性能
（1. State Key Laboratory of Advanced Design and Manufacture for Vehicle Body, Hunan University, Changsha 410082, China;
2. College of Materials Science and Engineering, Hunan University, Changsha 410082, China）
Abstract:The effect of Sr on microstructures and tensile properties of AZ91 Alloys were investigated by optical microscope, scan electron microscope and X-ray diffraction analyzer. The results show that Sr addition can refine and disperse the net-distributed eutectic structure, high-melting point Al4Sr phase with rob or blocky shaped morphology is observed at the grain boundaries of as-cast AZ91 alloy with Sr additions. AZ91-0.2Sr alloy obtains the best tensile properties comparing with AZ91 and other AZ91-Sr alloys. Comparing with AZ91 alloy, the occurrence of peak hardness of AZ91-0.2Sr alloy is delayed during the aging process. Because of the hard effects of the defined precipitated phase and high-melting point Al4Sr phase, AZ91-0.2Sr alloy after T6-treated also obtains the better tensile properties than that of the former AZ91 alloy at room temperature and 175 .
Key words: AZ91 Mg alloy; Sr; alloying; T6 treatment; microstructure; mechanical properties
