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以过共晶Al-20Si合金为研究对象,分析了P-RE复合变质剂的变质机理,测试了室温下铸态Al-20Si合金的拉伸性能,并对拉伸断口做了深入分析。试验表明,Al-20Si合金变质后,初生Si和共晶Si均得到明显细化,初生Si转变为近球形,共晶Si细化为粒状和短棒状。尺寸分别从100μm以上减小到10～15μm和1μm以下;室温拉伸试验表明,变质后合金强度提高了一倍。变质后Al-20Si合金的断口由细小的解理面和解理面之间的撕裂棱、韧窝组成,解理台阶之间聚集有大量韧窝带。
Based on the hypereutectic Al-20Si alloy, the deterioration mechanism of P-RE composite modifier was analyzed. The tensile properties of as-cast Al-20Si alloy at room temperature were tested and the tensile fracture was analyzed in depth. Experiments show that, Al-20Si alloy metamorphism, the primary Si and eutectic Si were significantly refined, primary Si into nearly spherical, eutectic Si refinement into granular and short rod-like. The size of the alloy decreased from above 100μm to below 10μm and below 1μm respectively. The tensile test at room temperature showed that the strength of the alloy was doubled after modification. After the metamorphism, the fracture of Al-20Si alloy consists of tearing edges and dimples between the small cleavage plane and the cleavage plane, and a large number of dimples gather between cleavage steps.