The T₁-precipitates and δ′/θ′/δ′ composite precipitates are the two primary strengthening precipitates and co-exist in the age-hardened 3rd generation AlLi alloys. The relative proportion of these two types of precipitates formed in the alloys is strongly dependent of the thermo-mechanical-treatment (TMT) processes applied. In the present study, using electron microscopy and properties characterization, the competitive precipitation behaviors of these two types of precipitates in an Al-4.0Cu-0.9Li-0.2Mg (wt.%) alloy, and the property of the alloy were investigated systematically in relation to TMT processes employed. It is shown that a 5% pre-deformation can promote the formation of T₁ precipitates but depress the δ′/θ′/δ′ composite precipitates, which improves the strength but decreases the plasticity of the alloy significantly. A pre-natural-aging will promote the fine δ′/θ′/δ′ composite precipitates and T₁ precipitates to form uniformly during subsequent artificial aging, improving the strength while maintaining good plasticity. A pre-artificial-aging at 180 °C will depress the formation of T₁ precipitates, and greatly reduce the plasticity of the alloy. Our study indicates that when the T₁ and the δ′/θ′/δ′ precipitates are equally developed, the alloy may achieve optimized properties.

T ₁析出物和δ'/θ'/δ'复合析出物是两种主要的强化析出物，并共存于时效硬化的第三代Al Li合金中。在合金中形成的这两种类型的沉淀物的相对比例在很大程度上取决于所应用的热机械处理（TMT）工艺。在本研究中，使用电子显微镜和性能表征，这两种类型的沉淀物在Al-4.0Cu-0.9Li-0.2Mg（wt。％）合金中的竞争沉淀行为，并系统地研究了该合金的性能。关于采用的TMT流程。表明5％的预变形可以促进T ₁的形成析出但降低了δ'/θ'/δ'复合析出物，从而提高了强度，但显着降低了合金的可塑性。预先自然老化会促进细小的δ'/θ'/δ'复合沉淀物和T ₁沉淀物在随后的人工时效过程中均匀形成，从而在保持良好塑性的同时提高强度。180°C的人工时效会抑制T ₁析出物的形成，并大大降低合金的可塑性。我们的研究表明，当T ₁和δ'/θ'/δ'析出物均等发展时，该合金可实现最佳性能。