研究了不同变质元素(0.2%Sr、0.5%La和0.5%Nd)对Al-18%Mg2Si合金凝固组织及性能的影响。探讨了变质元素对Mg2Si形核的影响机理。结果表明:0.2%Sr和0.5%Nd对Mg2Si相的变质效果最佳,力学性能明显提升。基于经典凝固形核理论,建立了变质元素吸附形核模型,该模型解释了变质元素吸附毒化作用呈现峰值的特点,并可用于计算该峰值处变质元素的最优覆盖率。 The effects of different metamorphic elements (0.2% Sr, 0.5% La and 0.5% Nd) on the microstructure and properties of Al-18% Mg2Si alloy were studied. The effect of metamorphic elements on the nucleation of Mg2Si was discussed. The results show that 0.2% Sr and 0.5% Nd have the best modification effect on Mg2Si phase, and the mechanical properties are obviously improved. Based on the classical solidification nucleation theory, a metamorphic element adsorption nucleation model was established. The model explained the characteristic of peak adsorption of metamorphic elements and could be used to calculate the optimal coverage of metamorphic elements at the peak.