(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 510640)
摘 要: 研究局部挤压慢压射A356压铸件不同部位处的微观组织及冲击性能。结果表明：铸态下共晶Si粒子大多为纤维状或长针状，呈不均匀的网状分布，冲击吸收功在1.17~2.35 J的范围内变化后；经T6热处理后，团簇状Al-Si共晶相明显减少，共晶Si粒子呈现出粒状或短棒状，且细小均匀，Si粒子的长宽比和面积分数都有显著降低，冲击吸收功在1.45~3.80 J的范围内变化，比铸态有明显提高。分析2种情况下不同部位处的断裂方式，数学回归分析表明，冲击性能由二次枝晶间距和Si粒子长宽比共同决定。
关键字: A356压铸件；慢压射压铸；微观组织；冲击性能
（State Engineering Research Center for Metallic Materials Net-shape Processing,
South China University of Technology, Guangzhou 510640, China）
Abstract:The microstructures and impact properties of slow injection A356 die casting with partial squeeze were investigated. The results show that as for the as-cast castings, eutectic Si particles are characterized as fibrous or long acicular shape as well as in homogenous distribution, and the impact absorbed energy varies from 1.17 to 2.35 J. After T6 heat treatment, the eutectic Si particles become small granular or short bacilliform, and the aspect ratio and area fraction of Si particles decrease evidently. The energy of the T6-treated castings is 1.45−3.80 J, which is higher than that of the as-cast castings. Furthermore, the fracture mechanisms of different regions in the castings were analyzed and discussed. Through mathematical regression analysis, it is indicated that the impact property depends on both the aspect ratio and secondary dendrite arm spacing of the Si particles.
Key words: A356 casting; slow injection die casting; microstructure; impact property
