中文摘要：

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%。

英文摘要：

The microstructures and properties of squeeze casting hypereutectic Al-17.5Si alloy after hot extrusion were analyzed.The results show that there are some effects of squeeze casting parameters on the microstructure of hypereutectic Al-17.5Si alloy,and the eutectic structure is refined significantly,and coralline eutectic Si phase is transformed into small needle-like ones.With the squeeze casting pressure increase,the coarse primary Si phases are reduced significantly and theα-Al dendrites are generated with more developed shape.After hot extrusion,microstructures of the squeeze casting hypereutectic Al-17.5Si alloy is changed greatly,and the absence of developedα-Al dendrite can be observed,and the small needle-like eutectic Si phases are broken into particles,and then are dispersed uniformly in the matrix of alloy after severe deformation.After hot extrusion forming,the properties of the squeeze casting hypereutectic Al-17.5Si alloy are improved greatly,especially the plasticity.After the hot extrusion forming of the squeeze casting billets at 320 MPa,tensile strength and elongation of the alloy reach158.82 MPa and 11.65%,respectively,which are increased by 84.13% and 441.86%,compared with those of the casting alloy.