Study of icosahedral quasi-crystalline phase T2-Al6CuLi3 and transformation in 2A97 Al-Li alloy fabricated by laser additive manufacturing.

[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]