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对过共晶Al-17.5Si合金热挤压成形后的组织与性能进行了研究。结果发现,挤压铸造Al-17.5Si合金的共晶组织明显细化,板片状的共晶Si相变为细小珊瑚状。并且,随着挤压比压的增大,粗大的初生Si相显著减少,α-Al枝晶越来越发达。对其进行热挤压后,发达的α-Al枝晶消失,细小珊瑚状的共晶Si相完全破碎为小粒状弥散分布在基体中。其力学性能大幅提高,塑性得到显著的改善。在320 MPa比压下铸造的坯锭再经热挤压成形后,其抗拉强度和伸长率分别达到158.82 MPa和11.65%,比重力铸造的分别提高了84.13%和441.86%。
The microstructure and properties of hypereutectic Al-17.5Si alloy after hot extrusion were studied. The results show that the eutectic microstructure of squeeze-cast Al-17.5Si alloy is obviously refined, and the plate-like eutectic Si phase changes into fine coral. Moreover, as the extrusion pressure increases, the coarse primary Si phase decreases significantly and the α-Al dendrites become more and more developed. After hot extrusion, the developed α-Al dendrites disappear and fine coral-like eutectic Si phases are completely broken into small particles dispersedly distributed in the matrix. Its mechanical properties increased significantly, plasticity has been significantly improved. The tensile strength and elongation of cast billet cast at 320 MPa were 158.82 MPa and 11.65%, respectively, which were 84.13% and 441.86% higher than that of gravity casting respectively.