Influence of Cu and Li Content on As-Cast Second Phase Features and the Dissolution during Homogenization of Al-Cu-Li Alloys

The influence of Cu and Li content on the formation and evolution of the second phase in Al-Cu-Li alloys was investigated under as-cast conditions and homogenization treatment regimes. The second phase was characterized via SEM, EDS, XRD and DSC analysis. The results revealed that elevated Cu content promoted the formation of all three resolvable phases in the as-cast microstructures. Increased Li content significantly enhanced the Al 7 Cu 4 Li phases while suppressing the Al 2 Cu phases. During the homogenization treatment, the low-melting-point AlCuMgAg eutectic structure exhibited preferential dissolution kinetics and higher temperatures facilitated the complete dissolution of both Al 7 Cu 4 Li and Al 2 Cu phases. The double-step homogenization treatment of 495°C/24 h+515°C/24 h is universally applicable to all the investigated alloys in this study.