(1. 中南大学 材料科学与工程学院，长沙 410083；
2. 广东省材料与加工研究所，广州 510650；
3. 华南理工大学 国家金属材料近净成形工程技术研究中心，广州，510641；
4. 柳州职业技术学院 机电工程学院，柳州 545005)
摘 要: 通过光学显微镜(OM)、扫描电镜(SEM)、拉伸性能测试和DSC差热分析等方法系统研究Al-5Ti-1B、Sr、La、Ce对A356.1铝合金组织和性能的影响。结果表明：Al-5Ti-1B对A356.1合金中初生α(Al)晶粒的细化作用十分显著，而对共晶硅和富铁相没有明显变质作用。Sr能有效地将A356.1合金中粗大、狭长的板条状转变为细小的颗粒状和短纤维状，从而大幅降低共晶硅的长度，并显著改善共晶硅的形状系数，但对初生α(Al)相和富铁相没有明显的细化变质作用。La、Ce对A356.1合金中初生α(Al)、共晶硅和富铁相均有一定的细化变质作用，但细化效果远不及Al-5Ti-1B，变质效果明显不如Sr。加入RE元素后，富铁相的形态未发生明显变化，但长度大幅减小，说明RE对富铁相的长大具有显著的抑制作用。当采用Sr变质时，合金的综合力学性能达到最佳，其中伸长率较添加Al-5Ti-1B、La、Ce时的分别提高56.8%、32.7%和21.1%。
关键字: 变质处理；A356铝合金；微观组织；力学性能
（1. School of Materials Science and Engineering, Central South University, Changsha 410083 China;
2. Guangdong Institute of Materials and Processing, Guangzhou 510650, China;
3. National Engineering Research Centre of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou 510641, China;
4. School of Mechanical and Electrical Engineering, Liuzhou Vocational and Technical College, Liuzhou 545005, China）
Abstract:The effects of Al-5Ti-1B, Sr, La and Ce on structures and properties of A356.1 aluminum alloy were investigated by optical microscopy (OM), scanning electron microscopy(SEM), tensile test and DSC differential thermal analysis systematically. The results show that Al-5Ti-1B has remarkable effect on the refinement of primary α(Al) grains in A356.1 alloy, but it has no obvious modification effect on eutectic silicon and iron-rich phase. Sr can effectively transform the thick and narrow strips into fine grains and short fibers in A356.1 alloy, thus it can greatly reduce the length of eutectic silicon and significantly improve the shape coefficient of eutectic silicon, but it has no obvious refining and modification effect on primary α(Al) phase and iron-rich phase. Both La and Ce can refine and modify the primary α(Al), eutectic silicon and iron-rich phase in A356.1 alloy, but its refinement effect is less than that of Al-5Ti-1B, and its modification effect is obviously less than that of Sr. After adding RE element, the morphology of iron-rich phase does not change substantially, but its length decreases significantly which indicates that RE have a remarkable inhibition on the growth of iron-rich phase. The comprehensive mechanical properties of the alloy that added Sr achieve the best. Compared with the Al-5Ti-1B, La and Ce, the elongation of the A356.1 alloy that modified by Sr is increased by 56.8%, 32.7% and 21.1%, respectively.
Key words: modification; A356 Al alloy; microstructrue; mechanical property
