In this work, the effects of the Cu/Li ratio on the mechanical properties and corrosion behavior of Sc-containing Al-Cu-Li alloys were systematically investigated by utilizing age-hardening behavior, tensile property, corrosion behavior, and electrochemical behavior, complemented by microstructural characterization through EBSD and TEM. The results show that the peak aging strength of the alloys remained relatively consistent but slightly decreased with the decrease in Cu/Li ratio, and the yield strengths were 585 MPa, 578 MPa, and 573 MPa, respectively. The changes in the Cu/Li ratio caused different matching patterns of precipitates in the peak aging alloys. The cumulative precipitation strengthening by T₁, θ′, δ′, and S′ phases are equal within the alloys with different Cu/Li ratios. However, the strength contribution of the T₁ phase decreases from 81% to 66% with the decrease in the Cu/Li ratio. Concurrently, the precipitates of LAGBs gradually increase in number and are continuously distributed, and the precipitates of HAGBs become larger in size with lower Cu content as the Cu/Li ratio decreases, all of which leads to a weakening of the intergranular corrosion (IGC) resistance within the low Cu/Li ratio alloy.

The influence of Cu content (3.10, 3.50, and 3.80 wt.%) on the precipitation behavior and mechanical properties of Al-Cu-Li alloys under two aging conditions (direct aging at 175 °C vs. 3.5% pre-stretching followed by aging at 155 °C) was systematically investigated. The alloys were characterized using hardness testing, tensile property evaluation, and transmission electron microscopy (TEM) to correlate microstructural evolution with performance. The results revealed that increased Cu content accelerated early-stage hardening kinetics and elevated peak hardness and strength. Aging at 175 °C/36 h produced T₁ phase-dominated microstructures with θ′ phases. With the increase of Cu content, the enhancement effect on the precipitation of T₁ and θ′ phases becomes more pronounced, gradually overshadowing the initial promotion effect on precipitate growth. Pre-deformation prior to 155 °C/36 h aging induced significant T₁ phase refinement and proliferation, with increasing Cu content continuously reducing T₁ phase sizes while moderately enlarging θ′ precipitates. Precipitation-strengthening analysis revealed a transition in T₁ strengthening from bypass to shearing dominance under 155 °C/36 h aging after pre-deformation, enhanced by Cu-promoted T₁ refinement, which collectively drove superior strength in high-Cu alloys. These findings provide valuable insights for the composition design and mechanical property optimization of Al-Cu-Li alloys.

In this work, the effect of Fe and Si content on microstructure, mechanical properties, and corrosion resistance of 7050 alloy was systematically investigated by room temperature tensile, fracture toughness, and exfoliation corrosion tests, complemented by microstructural characterization through SEM and TEM. The results demonstrate that the impurity elements Fe and Si induce the formation of insoluble Fe-rich phases and Mg₂Si phases in the alloy, respectively. The coexistence of Fe and Si leads to a severe synergistic deterioration effect on mechanical properties. Furthermore, the study reveals that Si has a more profound negative impact on mechanical properties than Fe. While Fe primarily reduces ductility and fracture toughness by initiating microcracks through Fe-rich phases with minimal effect on strength, Si not only forms brittle Mg₂Si phases that impair toughness but also significantly depletes the Mg content in the matrix, thereby reducing the quantity of strengthening phases. This results in a comprehensive and severe decline in strength, plasticity, and toughness. In addition, Fe and Si impurities markedly degrade the exfoliation corrosion resistance of the alloy.

This study systematically investigates the synergistic effects of the pre-stretching deformation and aging temperature on the precipitation behavior and mechanical properties of an Al-Cu-Li alloy. The results indicate that increasing the pre-stretching deformation significantly refines and increases the number density of T₁ and θ′ phases while optimizing the grain boundary precipitate morphology, thereby enhancing the fracture toughness and fatigue resistance without compromising the high strength. In contrast, elevating the aging temperature promotes the coarsening of the T₁ phase, inhibits θ′ precipitation, and coarsens the grain boundary precipitates, leading to a deteriorated damage tolerance. By matching 3.5~4.5% pre-stretching with 145~155 °C aging, a synergistic optimization of ultra-high strength and damage tolerance can be achieved.

Al-Li alloys can be strengthened by pre-stretching before artificial aging to promote the precipitation of the strengthened phase. This study investigates the mechanical properties and evolution of a 2 mm thick Al-Cu-Li alloy sheet’s microstructure with various pre-stretching degrees. From the results, as the degree of pre-stretching is increased, the strength gradually increases. Particularly noticeable is the upward trend in yield strength. By the pre-stretching volume of 4%, tensile strength can be enhanced by 95 MPa and yield strength by 187 MPa. Pre-stretching leads to a gradual reduction in precipitation of θ′, an increase in T₁ phase number density but a reduction in T₁ phase diameter. Meanwhile, a combination of strain-hardening and precipitation-strengthening determines the yield strength. Increasing the pre-stretching degree increases strain-hardening, while T1 phase strengthening decreases gradually.

This study systematically investigates the effects of Fe and Si impurities on the microstructure and mechanical properties of Al-Cu-Li alloys. Five alloy compositions with controlled Fe (0.03–0.12 wt.%) and Si (0.03–0.12 wt.%) contents were fabricated and processed through homogenization, hot extrusion, solution treatment, and aging. Microstructural characterization demonstrates that Fe promotes the formation of coarse skeletal Al₇Cu₂Fe intermetallics, while Si facilitates the precipitation of blocky α-AlFeSi phases and eutectic Si particles. An elevated Fe content substantially deteriorates strength, ductility, and fracture toughness, primarily due to two mechanisms: the persistence of thermally stable impurity phases that serve as stress concentrators and preferential crack initiation sites throughout thermomechanical processing, and the consumption of Cu that reduces the volume fraction of primary T₁ (Al₂CuLi) strengthening precipitates. In contrast, Si exhibits comparatively moderate detrimental effects. The findings establish that stringent Fe control is essential for maintaining mechanical performance, whereas strategic Si adjustment offers a viable approach for cost management in recycled alloy production.