Microstructure and Mechanical Properties of the As‐Cast AlLiCuMgZr Alloy with High Li Content and Different Cu/Mg Ratios

The microstructures and mechanical properties of as‐cast AlLiCuMgZr alloys with high Li content and different Cu/Mg ratios are investigated. The results show that the tensile strength increases and the elongation almost keeps unchanged, with the decrease in Cu/Mg ratio. The tensile fracture exhibits typical intergranular fracture. The main phases of as‐cast alloys are α(Al), δ′(Al 3 Li), and T 2 (Al 6 Li 3 Cu). With the decrease in Cu/Mg ratio, the size of the δ′(Al 3 Li) phase increases, and the amount of T 2 (Al 6 Li 3 Cu) phase at the grain boundary decreases. Moreover, the fine S 1 (Al 2 MgLi) phase and S′(Al 2 CuMg) phase are formed inside the grains near the grain boundaries. The improved properties are attributed to the solution strengthening and second‐phase strengthening of δ′(Al 3 Li).