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

• Published in: Journal of alloys and compounds 2025-01, Vol.1010, p.177927, Article 177927
• Main Authors: Li, Guoqing, Bai, Pucun, Sun, Yuewen, Liu, Fei, Cui, Xiaoming
• Format: Article
• Language: English
• Subjects: Al-Cu-Mg-Li-Sc alloy; Al3Li (Al3Sc) core-shell structures; Atom probe tomography; Heat treatment; Microstructure
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2024.177927

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 θ-phase (Al2Cu), numerous Al3Sc phases, Al3Li phases, and Al3Li (Al3Sc) core-shell structures—L12-type ordered and fully coherent with the α-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. •The precipitation behavior of precipitated phases of Al-Cu-Mg-Li-Sc alloys at 490 °C/1 h+ 190 °C/ (2, 14, 24) h was investigated.•Theoretical structural models of the Al3(Li, Sc) core-shell structure precipitated during heat treatment of Al-Cu-Mg-Li-Sc alloys have been investigated using HRTEM and APT characterization techniques.•Using APT characterization, it was found that some Li atoms in the Al-Cu-Mg-Li-Sc alloy replace some of the Mg atoms in the S-phase (Al2CuMg) to form the S-like phase of Al2CuMg2/3(Mg Li)1/3.