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采用稀土Sc对A356合金进行变质处理,研究了Sc对A356合金的初生α相和共晶硅形态及其力学性能的影响。结果表明:加入Sc在铝熔体中生成Al3Sc可以作为α-Al的非自发形核的核心,显著细化A356合金中的初生α相,由粗大的树枝晶形态变为细小的短枝晶和圆整的颗粒状形态,同时,Sc对共晶硅也具有显著的变质作用,使其由粗大的针片状变为细小的纤维状和蠕点状。当Sc的加入量为0.2%(质量分数)时,对A356合金中初生α相的细化作用和对共晶硅的变质作用即可达到最佳的效果,合金的铸态抗拉强度和伸长率分别提高23.7%和58.1%,在此基础上,继续增加Sc的加入量,对进一步改善合金微观组织和力学性能的作用不显著。
A356 alloy was modified by rare earth Sc to study the effect of Sc on the morphology and mechanical properties of primary α phase and eutectic silicon of A356 alloy. The results show that the addition of Sc to Al3Sc in aluminum melt can be used as the core of α-Al non-spontaneous nucleation. The primary α phase in A356 alloy is significantly refined and the coarse dendritic morphology is changed into small short dendrite and Round granular morphology, at the same time, Sc of eutectic silicon also has a significant metamorphism, making it from the coarse needle-like into small fibrous and creep-like. When the addition amount of Sc is 0.2% (mass fraction), the fine effect of the primary α phase in A356 alloy and the metamorphism of eutectic silicon can be achieved the best effect. The as-cast tensile strength and elongation The rate of increase of 23.7% and 58.1% respectively, on the basis of which, adding the amount of Sc continuously has no significant effect on further improving the microstructure and mechanical properties of the alloy.