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该文借助金相、电镜和热分析等手段，研究微量混合稀土（０．０５％～０．５０％，质量分数）对Ａｌ－７Ｓｉ－４Ｃｕ合金铸态组织与硬度的影响。结果表明，凝固速度显著影响稀土对共晶硅相的变质效果，稀土减小α（Ａｌ）二次枝晶间距，并使合金铸态硬度提高。微量稀土富集于α（Ａｌ）－Ｓｉ相界α（Ａｌ）－Ａｌ２Ｃｕ相界甚微。试验证实，稀土使合金中花纹状三元共晶α（Ａｌ）＋Ｓｉ＋Ａｌ２Ｃｕ减少，块状Ａｌ２Ｃｕ相增加
In this paper, the microstructure, hardness and hardness of the as-cast Al-7Si-4Cu alloy were investigated by means of metallography, electron microscopy and thermal analysis. The effects of micro-mischmetal (0.05% ~ 0.50% The results show that the solidification rate significantly affects the modification effect of rare earth on the eutectic silicon phase. The rare earth decreases the secondary dendritic spacing of α (Al) and increases the as-cast hardness of the alloy. Trace rare earth enriched in the α (Al) -Si phase boundary α (Al) -Al2Cu phase boundary is minimal. Experiments confirmed that the rare earth alloy in the pattern of ternary eutectic α (Al) + Si + Al2Cu reduce block Al2Cu phase increases