Structures and Properties of Nano–Precipitates in Al–Li Alloys
WANG Shuo 1 , ZHANG Chi 1 , WANG Junsheng 1,2
(1. School of Materials Science & Engineering, Beijing Institute of Technology, Beijing 100081, China; 2. Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, Beijing 100081, China)
Abstract：The structure and performance of the third and fourth generation Al–Li alloys depend on the type, size, shape, distribution and sequence of the nano–precipitates within them. In this review paper, typically nano–precipitates generated by additions of Mg, Ag, Si, and Mn elements were reported. In particular, in Al–Li–Cu system: stabilities of δ′ (Al3Li) and δ′(Al3Li)/Al3Sc core–shell structures with non–equilibrium composition; the coherent and semi–coherent interfaces of θ′(Al2Cu)/α–Al and the segregation behavior of Cu at the interfaces; the origin of the relationships including “in–phase” and “anti–phase” for opposite δ' phases in the δ′/θ′/δ′ composite precipitation; and various crystal structure models of T1 (Al2CuLi). In Al–Li–Cu–Mg system: the interface of S(Al2CuMg)/α–Al; the good resistance of Ω(Al2Cu) phases to grain coarsening and the nucleation induced by vacancy. In the Al–Li–Cu–Mg–Si system: the competitions for σ(Al5Cu6Mg2) – S' and σ–Ω due to non–component Si and Ag atoms; and phase transition from Q(Al3Cu2Mg9Si7) to B'(Al3Mg9Si7) because of the intrinsic point defect in Q. By using X–ray diffraction (XRD), high–resolution transmission electron microscopy (HRTEM), high–angle annular dark–field scanning transmission electron microscopy (HAADF– STEM), and first–principle calculations, it is able to provide inspiration for us to understand the performances of these nano precipitations.
2021, 
