(华南理工大学 机械与汽车工程学院，广州 510640)
摘 要: 研究在不同挤压力下凝固的Al-Si-Cu-T4的显微组织和力学性能。结果表明：在挤压力下凝固时，该合金显微组织发生明显变化，其抗拉强度和伸长率均有明显提高。当挤压力为0.1~50 MPa时，随着挤压力的增加，初生α(Al)晶粒尺寸和共晶Si粒子长宽比均显著减小，Si相形貌由长针状变成粒状或圆棒状。同时，枝晶间距减小，Al2Cu相量和枝晶间孔洞数量减少，力学性能提高；而当挤压力为50~100 MPa时，挤压力的增加对合金显微组织和力学性能影响不大。因此，50 MPa为该合金的合适挤压力，在该条件下凝固的合金经T4热处理后，其抗拉强度和伸长率分别为323.6 MPa和8.51%。此外，分析讨论了不同挤压力下凝固的合金断口裂纹的形成。
关键字: Al-Si-Cu合金；挤压铸造；力学性能；微观组织
Al-Si-Cu-T4 solidified at different squeeze pressures
（School of Mechanical and Automotive Engineering, South China University of Technology,
Guangzhou 510640, China）
Abstract: Microstructures and mechanical properties of Al-Si-Cu-T4 solidified at different squeeze pressures were investigated. The results show that at the pressures applied during solidification, the microstructures of the alloy change significantly, and both tensile strength and elongation of the alloy are improved remarkably. When the squeeze pressure increases from 0.1 MPa to 50 MP, the size of primary α(Al) and aspect ratio of eutectic Si phase are decreased evidently and the morphology of eutectic Si particles is changed from long acicular to small granular, and the dendrite arm spacing, content of Al2Cu phase and porosities between dendrites are decreased, while the mechanical properties are increased. When the squeeze pressure increases from 50 MPa to 100 MPa, the microstructure and mechanical properties of the investigated alloy show little variation. It is indicated that the proper squeeze pressure of the investigated alloy is 50 MPa at which the tensile strength and elongation reach to 323.6 MPa and 8.51%, respectively, after solution heat treatment. Furthermore, the crack origin of the investigated alloys solidified at different squeeze pressures was analyzed and discussed.
Key words: Al-Si-Cu alloy; squeeze casting; mechanical property; microstructure
