Effect of grain thickness and T1 precipitate on the strength anisotropy of Al-4.0Cu-1.0Li-0.4Mg-0.4Ag-xZr alloys under different heat treatment

The influences of grain thickness and T1 precipitate on the strength anisotropy of extruded Al-4.0Cu-1.0Li-0.4Mg-0.4Ag-xZr alloys (x = 0, 0.1, and 0.14 wt%) were investigated. The alloys were subjected to different heat-treatment conditions to obtain distinct grain morphologies adjusted by different Zr content and to induce T1 precipitate. The results demonstrated that grain morphology, particularly the grain thickness influenced by various Zr content, is the primary factor affecting strength anisotropy under different heat treatment conditions. In solution heat-treated alloys (SHT), reduced grain thickness, extended length of low-angle grain boundaries (LAGBs), and more uniformly distributed dislocations due to increasing Zr content led to a decrease in strength anisotropy. Conversely, in T6-aged alloys, the combined interaction between T1 precipitate and substructures in thinner grains with more LAGBs may aggravate the degree of strength anisotropy. In addition, the T1 precipitate further amplified the anisotropy induced by the Brass texture component also increasing strength anisotropy. The findings highlight the significance of grain thickness, LAGBs length, dislocation distribution, and the interaction between T1 precipitate and these factors in influencing the strength anisotropy of Al-Li alloys. Moreover, after solution heat treatment, adding 0.1 wt% Zr in the alloy reinforced the intensity of beta-fiber texture while adding 0.14 wt% Zr wakened the beta-fiber texture intensity due to the particle-simulated recrystallization process.