Effect of Li Content on the Microstructure and Corrosion Behavior of Homogenized Al–Cu–Li Alloys

The microstructure and corrosion behavior of Al–Cu–Li alloys with different Li contents before and after homogenization have been investigated. The results show that before homogenization, the coarse second phase evolves from θ  +  T _B to T ₁  +  T _B phase, combined with some AlCuFe and AlCuFeMn particles, with the increase in Li content. After homogenization, numerous phases were dissolved back into the matrix when the Li content was low, but the T ₁ phase still remained in the alloy with higher Li content. Increased Li content remarkably increased the corrosion susceptibility of both the as‐cast and the homogenized alloy, and the corrosion mode evolved from pitting to inter‐granular corrosion. With increasing Li content, active T ₁ phases were formed as a network structure at grain boundaries, which led to a sharp rise in IGC sensitivity. After homogenization, there were still some T ₁ observed at grain boundaries, andsome dissolved Li solutes could also be preferentially segregated at grain boundaries. The severe intergranular corrosion observed in the homogenized Al–Cu–Li alloys with 1.9 and 2.4 wt.% Li appears to be associated with the segregation of Li, the aggregation of T1 phases, and the increased activity of AlCuFe and AlCuFeMn phases.