Yb和Al-Ti-B复合变质对过共晶Al-Si铸造合金组织和性能的影响

Influence of Yb and Al-Ti-B complex modification on the microstructure and performance of hypereutectic Al-Si casting alloys

摘要:

采用光学显微镜、扫描电子显微镜、电子探针,研究了不同比例的稀土Yb和Al-5Ti-B复合变质剂对过共晶Al-20Si合金显微组织与性能的影响。结果表明,Al-20Si合金中添加0.5% Yb和0.3% Al-5Ti-1B复合变质剂使得粗大的多边形状、块状和五瓣星状初生Si变质为细小块状,共晶Si由粗大的片状或针状结构变质为细小颗粒或者纤维结构,而且粗大的α-Al枝晶被细化为等轴枝晶。然而,当Al-5Ti-B变质剂含量达到0.4%时,初生Si和共晶Si出现粗化现象。力学性能测试结果表明,合金的抗拉强度和延伸率分别增加了83.7%和92.1%。

Abstract:

In this study, the microstructure evolution and mechanical properties of hypereutectic Al-20Si alloy containing rare earth Yb and Al-5Ti-1B refiner were investigated. The microstructures of the samples were characterized by optical microscopy, scanning electron microscopy, and electron probe microanalysis. Microstructural analysis demonstrated that the primary Si was significantly refined from a coarse polygonal, platelet-like or star-like shape into a fine blocky shape; the eutectic Si structure was modified from a coarse platelet-like/needle-like structure into fine particles or a fibrous structure; and the coarse α-Al dendrites were refined into fine equiaxed dendrites after the addition of 0.5% Yb and 0.3% Al-5Ti-1B complex. However, the primary and eutectic Si phases became coarser when the content of Al-5Ti-1B refiner reached 0.4%. The mechanical properties of the Al-20Si alloy with different modifiers and different modifier concentrations were investigated with the tensile test. The results showed that the ultimate tensile strength and elongation of the prepared sample increased by 83.7% and 92.1%, respectively.