Effect of Sc and Zr on Microstructure and Mechanical Properties of As-Cast Al–Li–Cu Alloys

Effect of Sc and Zr addition on microstructure and mechanical properties of as-cast Al–Li–Cu alloys are investigated. The results show that, a significant grain refinement can be caused by Sc and Zr. The coarse dendritic microstructure is transformed into equiaxed grains after adding Sc and Zr. The refinement can be attributed to the primary particles, Al₃ (Sc,Zr), of which the orientation is close to that of α-Al matrix. The primary particles prevent the unsuitable diffusion and act as heterogeneous nucleation sites for α-Al in the process of solidification. The model for the multi-layer structure evolution of primary particle is established. Moreover, the mechanical properties of as-cast Al–Li–Cu–Sc–Zr alloy are affected markedly because of the addition of Sc and Zr. The solid solution strengthening and Hall–Petch strengthening are primary strengthening mechanisms, YS = Δσ_HPS + Δσ_sss + 104 (MPa).