Precipitation behavior and phase stability in Al-Cu-Mg-Li-Sc alloy during aging

This study investigates the precipitation behavior and phases stability in Al-Cu-Mg-Li-Sc alloy during aging, using scanning electron microscopy (SEM), high- resolution transmission electron microscopy (HRTEM), and atom probe tomography (APT). Results show that, besides the precipitation of S-phase (Al2CuMg) and theta-phase (Al2Cu), numerous Al3Sc phases, Al3Li phases, and Al3Li (Al3Sc) core-shell structures-L12-type ordered and fully coherent with the alpha-Al matrix-form in the alloy after aging in the presence of Li and Sc elements. With increasing aging time, both Al3Sc and Al3Li (Al3Sc) core-shell structures maintain their morphology and structure, while also facilitating the formation of the alloy's primary strengthening phase, S. APT analysis further reveals that some Li atoms replace Mg atoms in the S phase, producing an S-like phase Al2CuMg2/3(Mg Li)1/3.