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研究了稀土镧和钇对过共晶铝硅合金的微观组织和力学性能的影响．实验合金为Ａｌ－２２％Ｓｉ，所加稀土为富镧混合稀土（含８０％Ｌａ）和Ａｌ－８８％Ｙ中间合金，加入量分别为０．６％～１．４％Ｌａ和０．１０％～０．１８％Ｙ．合金熔化精炼后在预热至２５０°Ｃ的金属型中浇铸成１２ｍｍ×６０ｍｍ试棒，浇注温度７４０°Ｃ．高温力学性能测试３００°Ｃ下保温３０ｍｉｎ后的拉伸强度．实验结果表明：单独加入稀土不能细化初晶硅，结合磷的作用，镧、钇可实现初晶硅和共晶硅的双重变质，其中初晶硅可细化至２２μｍ左右；适量Ｌａ可形成有利于提高高温性能的Ａｌ５ＳｉＣｕ２Ｌａ化合物；Ｙ可以有效地抑制该化合物长成粗大针状．经淬火及稳定化回火热处理后，合金室温抗拉强度可达２７６ＭＰａ，高温强度可达１７４ＭＰａ．
The effects of rare earth lanthanum and yttrium on the microstructure and mechanical properties of hypereutectic Al-Si alloys were investigated. The experimental alloys were Al-22% Si. The rare earths were La-rich mixed rare earths (containing 80% La) and Al-88% Y master alloys with additions of 0.6% -1.4% La and 0.10% % ~ 0.18% Y. After melting the alloy in the preheated to 250 ° C in the metal cast into 12mm × 60mm test bar, casting temperature 740 ° C. Tensile strength after 30min incubation at 300 ° C is tested at high temperature mechanical properties. The experimental results show that the addition of rare earth can not refine the primary silicon, the combination of phosphorus, lanthanum, yttrium can be achieved dual-primary silicon and eutectic silicon metamorphism, in which primary silicon can be refined to about 22μm; appropriate amount of La can be formed Al5SiCu2La compound is beneficial to improve the high temperature performance; Y can effectively inhibit the compound grow into a thick needle. After quenching and stabilization tempering heat treatment, the alloy tensile strength up to 276MPa room temperature, high temperature strength up to 174MPa.