Junsheng Wang
1 School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
2 Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, Beijing 100081, China

EXTENDED ABSTRACT: The size distribution and structural evolution of the precipitates are critical to the mechanical properties of heat treatable alloys. In Al-Li alloys, many studies have reported that monodisperse core—shell Al3Li/AliZr, Sc) structures in a Li-rich enviromnent promote formation of o'-Al3Li, Tl-Al2CuLi, and 8'-Al2Cu precipitates. However, without quantitative measurements of the precipitate size distribution and tracking their crystal structure evolution, the kinetics of Li­rich clusters and excessive Li diffusion into monodisperse core—shell Al3(Zr, Sc) structures in Al alloys to prevent Li­-cluster coarsening is largely unknown. In this presentation, in-situ small angle neutron scattering (SANS) has been adopted to track the evolution of O-Al3Li precipitates. Upon quenching, Li-rich clusters remain at a smaller size and higher number density. Once aging starts, nucleation of o'-Al3Li precipitates on top of Ali Zr, Sc) is at the expense of dissolution of those Li-rich clusters below the critical size. From density functional theory (DFT) calculations, it has been found the 6'-Al3Li precipitate nucleation barrier on top of Ali Zr, Sc)s negligible, as well as the nucleation barrier of -Al2Cu on top of AliZr, Sc) is much lower relative to that on -AL Besides, the substitutional energy for Li to replace Zr and Sc sites in AllZr, Sc) is favorable. Combining SANS with high-resolution transmission electron microscopy (HRTEM), the effects of AliZr, Sc) cores on preventing o'-Al3Li size from coarsening by absorbing Li to form Al3(Li, Zr, Sc) have been uncovered. Simultaneously, the contributions of AllLi, Sc, Zr) particles and'-Al3Li to the strength has been quantified and new alloys have been designed to utilize the precipitating kinetics at the presence of monodisperse precursors for industrially relevant light-weight structural Al-Li alloys.

Keywords: Al-Li; Precipitation; SANS; DFT; HRTEM; ICME
References
[l] C. Xue, S. Wang, Y. Zhang, G. Tian, X. Yang, X. Chang, Y. Ke, Z. Xie, J. Wang*, Mater. Sci. & Eng. A 881 (2023) 145393