在铸造A390铝合金中,加入混合稀土作为变质剂,采用光学显微镜研究了变质剂对组织的影响。结果表明,A390合金经混合稀土变质后,初生硅棱角钝化,尺寸明显减小;其变质效果与变质剂的加入量有关,当加入0.24%的混合稀土时,效果最为显著,初生硅尺寸由原来的175μm减小到28μm左右,并简要探讨了其变质机理。 In the cast A390 aluminum alloy, mixed rare earth was added as a modifier, and the effect of the modifier on the microstructure was studied by optical microscope. The results show that the A390 alloy is passivated by mixed rare earths, the primary silicon edge is passivated and its size is obviously reduced. The modification effect of A390 alloy is related to the addition amount of modifier. When 0.24% rare earth is added, the effect is most obvious. The original 175μm is reduced to about 28μm, and its metamorphic mechanism is briefly discussed.