An Ultrastrong Multilayer Core-Shell Nanostructure in Aluminum-Lithium Castings

Al-Li alloys with a high Li content have the advantages of low density and high stiffness but usually suffer from poor strength, instability of nanoprecipitates, and severe anisotropy, limiting their practical application. Here, we introduce a stable multilayer core-shell nanostructure in aluminum-lithium alloy castings to address these challenges. By quantifying the precipitates' composition and structures using atom probe tomography (APT) and small angle neutron scattering (SANS), it was found that there exists a unique type of Li-rich, coherent, nanoscale single-core double-shell particles in this alloy, which is different from the previously reported core-shell structures. First-principles calculations reveal that this complex core-shell structure possesses both the advantage of low mismatch-induced nucleation and highly stable characteristics under service conditions. Compared with traditional core-shell structures, this core-shell structure exhibits the lowest critical nucleation radius and free energy within the solidification range, enabling the cast Al-Li alloy to achieve a strength approaching 500 MPa.