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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] • A novel Al-Cu-Li-Mg-Ag-Sc alloy was fabricated by direct energy deposition. • Dual-phase strengthening of Al 3 Sc and T 1 phases can be achieved with a single-stage T6 heat treatment. • The excellent compressive yield strengths achieved 512, 345 and 227 MPa at 20, 200 and 300 °C, respectively. • Al 3 Sc and T 1 phases can maintain strong pinning effects on dislocations. In this work, precipitation and deformation behavior of a novel Al-Cu-Li-Mg-Ag-Sc alloy fabricated by direct energy deposition (DED) were investigated in detail. Dual-phase strengthening of Al 3 Sc and T 1 (Al 2 CuLi) phases can be achieved with a single-stage T6 heat treatment compared to normal double-aging. The excellent compressive yield strengths achieved 512, 345 and 227 MPa at 20, 200 and 300 °C, respectively. Al 3 Sc and T 1 phases can maintain strong pinning effects on dislocations, suggesting a good work hardening ability during deformation. [ABSTRACT FROM AUTHOR]