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[Display omitted] • A novel Al-Cu-Li-Mg-Ag-Sc alloy was fabricated by laser direct energy deposition. • The fully equiaxed grain structure of as-built alloy can be obtained by adding 0.3 wt% Sc. • The precipitation behavior of primary Al 3 Sc particles was studied based on transient nucleation theory. • T 1 , Al 3 Sc, T B , and quasicrystalline T 2 phases serve as primary strengthening phases. In this study, a novel Al-Li alloy with minor Sc addition was fabricated by laser directed energy deposition (LDED), resulting in a fully equiaxed grain structure. The precipitation behavior of primary Al 3 Sc particles was studied based on transient nucleation theory, and the results showed that sufficient heterogeneous nuclei by primary Al 3 Sc particles could preferentially form at initial solidification stage and induce into equiaxed grains. Besides, a large number of acicular T 1 (Al 2 CuLi) phases and spherical Al 3 Sc phases, as well as rod-shaped T B (Al 7 Cu 4 Li) phases and quasicrystalline T 2 (Al 6 CuLi 3) phases, were distributed in as-built alloy that served as primary strengthening phases by thermal cycling. However, the specific nucleation behavior of α-Al grains on primary Al 3 Sc particles and subsequent growth behavior during rapid solidification need to be further investigated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quasi-crystalline T 2 phase precipitates for 2A97 Al-Li alloy produced by laser additive manufacturing. • Under influence of thermal cycle, T 2 phase transforms into face-centered cubic Y phase. • T 2 phase turns into O phase with orthorhombic at 515 °C for 1.5 h during solution treatment. Precipitated phases of 2A97 Al-Li alloy fabricated by laser additive manufacturing with thermal input are mainly composed of quasicrystal T 2 phase gathered around grain boundary and T B phase in grain interior. Diffraction patterns of quasi-crystalline T 2 phase show two-fold, three-fold and five-fold symmetry, respectively. Under condition of thermal cycling, T 2 phase transforms into a face-centered cubic Y phase with a lattice constant of 2 nm. Y phase can grow into twins, and the twin plane is (1 1 1). After solution treatment at 515 °C for 1.5 h, δ' phase, T 1 phase and T B phase are completely dissolved in matrix, while quasi-crystalline T 2 phase transforms into orthorhombic O phase. The size of O phase is similar to that of T 2 , with length of about 400 nm and rougher surface. [ABSTRACT FROM AUTHOR]