中文摘要：

采用金相显微镜（OM）、透射电镜（TEM）和拉伸力学性能测试等手段,研究了La和Pr复合变质对Al-Cu合金力学性能以及显微组织的影响,并分析了La和Pr的存在形式与作用机理。结果表明,不同时效温度下La＋Pr复合变质AlCu合金的峰值硬度都要高于未变质Al-Cu合金,165℃×10h为适宜的时效热处理制度;La＋Pr复合变质Al-Cu合金的常温抗拉强度和伸长率都要明显高于未变质Al-Cu合金,且0.2%的La＋0.1%的Pr复合变质Al-Cu合金的室温抗拉强度和伸长率取得最大值,高温抗拉强度和伸长率都要高于相同温度下未变质Al-Cu合金,其主要强化机制为细晶强化和第二相强化。

英文摘要：

The effects of La and Pr composite modification on the mechanical properties and microstructure of Al-Cu alloy were investigated by OM,TEM and tensile testing,and the existing forms and mechanism of La and Pr were described.The results reveal that the peak hardness of 0.3%（La＋Pr）composite modified Al-Cu alloy at different aging temperature is the higher than that of unmodified AlCu alloy,and the suitable aging treatment process is at 165℃for 10 h.The tensile strength and elongation at room temperature of La＋Pr composite modified Al-Cu alloy are significantly higher than those of unmodified Al-Cu alloy,and the tensile strength and elongation reach the maximum value with 0.2%La＋0.1%Pr composite modification on Al-Cu alloy,In addition,the tensile strength and elongation at high temperature are the higher than that of unmodified Al-Cu alloy at the same temperature.The main strengthening mechanism of 0.2%La＋0.1%Pr composite modified Al-Cu alloy belongs to fine grain strengthening and second phase strengthening.