(1. 上海交通大学 材料科学与工程学院，轻合金精密成型国家工程研究中心，上海 200240；
2. 上海纳特汽车标准件有限公司，上海 201111)
摘 要: 研究了微量Sr变质对Al-7Si-0.35Mg-0.1Ti合金微观组织和力学性能的影响，再以某汽车用压铸零部件为研究对象，通过数值模拟技术对0.06%Sr变质Al-7Si-0.35Mg-0.1Ti合金压铸工艺中的浇注温度和压射速度进行模拟计算，并进行实验验证。模拟结果表明：当浇注温度为680 ℃时，合金二次枝晶臂间距更小；随着压射速度的提高(1 m/s、2 m/s、4 m/s)，虽卷气现象更明显，卷气部位和数量更多，但气孔尺寸相对较小。压铸验证实验结果显示：随着压射速度从1 m/s提高到4 m/s，初生α(Al)相由胞状树枝晶部分转变为球状晶或近球状晶，且晶粒平均尺寸逐渐减小；铸件中卷气由大尺寸的气孔转变为小尺寸的缩孔疏松，与数值模拟结果基本一致。同时，铸件的抗拉强度和伸长率分别提升23.7%和188.5%，且合金断裂机制也由1 m/s时的大尺寸气孔起决定作用的脆性断裂转变为4 m/s时共晶Si相起决定作用的脆性断裂和韧性断裂的混合断裂模式。
关键字: Al-7Si-0.35Mg-0.1Ti合金；压铸；数值模拟；浇注温度；压射速度
（1. National Engineering Research Center of Light Alloy Net Forming, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
2. Shanghai NATE Automobile Fastener Co., Ltd., Shanghai 201111, China）
Abstract:The effects of micro Sr modification on the microstructure and mechanical properties of Al-7Si-0.35Mg-0.1Ti alloy were firstly studied. Then, the pouring temperature and injection speed of 0.06% Sr modified Al-7Si-0.35Mg-0.1Ti alloy in the die casting process were calculated by numerical simulation technology, and the experimental verification was carried out. The simulation results show that when the pouring temperature is 680 ℃, the secondary dendrite arm spacing is smaller; with the increase of injection speed (1 m/s, 2 m/s, 4 m/s), although the air entrainment is more obvious, the position and quantity of air entrainment are more, but the pore size is relatively small. The results of die casting verification experiment show that, with the increase of injection speed from 1 m/s to 4 m/s, the primary α(Al) phase changes from cellular dendrite to globular or near globular, and the average grain size decreases gradually; the volume gas in the casting changes from large-size pores to small-size shrinkage porosity, which is basically consistent with the numerical simulation results. At the same time, the ultimate tensile strength and elongation of the die casting alloys increase by 23.7% and 188.5%, respectively. And the fracture mechanism of the tested alloys changes from the brittle fracture determined by large pores at 1 m/s to mixed fracture mode of brittle fracture and ductile fracture determined by eutectic Si phase at 4 m/s.
Key words: Al-7Si-0.35Mg-0.1Ti alloy; die casting; numerical simulation; pouring temperature; injection speed
