The influence of rare earth Er additionits (mass ratio was 0% - 0. 3%) on 7055 aluminum alloy as-cast microstructure were studied by OM,SEM,EDS,XRD and microhardness testing. The results show that the effect of microstructure refinement heightened with the increasing of Er addition when Er addition was less than 0. 25wt%. The effect of grain refinement was most obviously when Er addition was 0. 25wt%, and it was 60% of the grain size without Er. Grain refinement weakened when Er addition was more than 0. 25wt%. The compounds of Alg Cui Er and a small quantity of AI3 Er formed and distributed along grain boundaries after Er added to alloy.%采用光学显微镜、扫描电镜、能谱仪、X射线衍射仪、显微硬度计等仪器研究了稀土铒加入量(质量分数为0％～0.3％)对7055铝合金铸态显微组织的影响。结果表明：当铒加入量小于0.25％时，随加入量增加组织细化效果增强；当铒加入量为0.25％时，晶粒细化效果最显著，晶粒尺寸是未加铒元素时的60％；当铒加入量超过0.25％后，晶粒细化效果减弱；铒加入合金中主要形成Al8Cu4Er和少量Al3Er化合物相并且主要分布在晶界上。
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