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采用金属型铸造方法,制备了不同RE含量的Al-4.5Zn-1.0Mg-0.8Cu合金。利用力学性能测试、OM、SEM及EDS等分析测试手段,研究了RE对Al-4.5Zn-1.0Mg-0.8Cu合金微观组织和力学性能的影响。结果表明,随着RE加入量的增加,合金的抗拉强度和伸长率均呈先增大后减小的趋势。在试验范围内,加入0.12%的RE(质量分数)时,合金具有最优的综合力学性能。加入适量RE可明显减小合金二次枝晶间距。RE主要偏聚在晶界和枝晶界处,以AlZnMgCuRE相形式呈短棒状存在。加入过量RE会对合金产生过变质作用,增大合金二次枝晶间距,AlZnMgCuRE相呈粗大的块状,割裂作用增加,降低合金的力学性能。RE还促进了Mg和Zn在Al中的固溶,增强了固溶强化作用。
Al-4.5Zn-1.0Mg-0.8Cu alloys with different RE contents were prepared by metal casting method. The effects of RE on the microstructure and mechanical properties of Al-4.5Zn-1.0Mg-0.8Cu alloy were investigated by mechanical testing, OM, SEM and EDS. The results show that with the addition of RE, the tensile strength and elongation of the alloy first increase and then decrease. Within the experimental range, the addition of 0.12% RE (mass fraction), the alloy has the best overall mechanical properties. Addition of RE can significantly reduce the secondary dendrite spacing. RE mainly segregated in the grain boundaries and dendrite boundaries, with AlZnMgCuRE phase was short rod-shaped existence. Addition of excessive RE can cause metamorphism of the alloy, increase the secondary dendrite spacing of the alloy, and the AlZnMgCuRE phase is coarse and massive, which increases the segregation effect and reduces the mechanical properties of the alloy. RE also promotes the solution of Mg and Zn in Al and enhances the solution strengthening effect.