关键词: Al-Si合金, Cu添加, 固溶处理, 微观组织, 力学性能

Abstract: Effect of Cu addition with different mass fraction(0%, 1%, 2%, 3%, 4%, 5%) on the solidification microstructure and mechanical properties of Al-20Si hypereutectic alloy was systematically investigated. Subsequently, the optimal solution treatment parameters for Al-20Si-3Cu alloy were explored. The results indicate that the addition of Cu element significantly refines the primary Si grain size and promotes the transformation of eutectic Si into granular morphology, and the θ-Al₂Cu phase emerges in the microstructure when Cu content reaches or exceeds 3%. The Al-20Si-3Cu alloy exhibits the smallest primary Si phase grain size of 93.76 μm and achieves the highest yield strength of (242±5) MPa, with the primary Si phase hardness reaching 1096.28 HV. After solution treatment, the primary Si phase in the Al-20Si-3Cu alloy exhibits rounded edges and the eutectic Si further spheroidizes. However, elevated solution temperature to 550 ℃ induces grain growth tendency, while prolonged treatment duration (10 h) causes overburning phenomenon and reduces roundness of primary Si, consequently decreasing hardness. Under the solution treatment condition of 525 ℃ for 10 h, the primary Si phase attains maximum hardness of 1140.69 HV and the hardness of eutectic Si phase reaches 99.82 HV. The comprehensive analysis concludes that the optimal solution treatment for the alloy is 525 ℃ for 10 h.

Key words: Al-Si alloy, Cu addition, solution treatment, microstructure, mechanical properties