针对Al-Cu-Li-Mg合金中自然时效对后续人工时效析出行为的影响机制问题，借助TEM、三维原子探针(3DAP)、三维重构(3DET)及力学性能测试等实验方法，系统研究了自然时效对Al-2.95Cu-1.55Li-0.57Mg-0.18Zr合金在160℃人工时效时微观组织及力学性能的影响。结果表明，自然时效形成的富Mg或Cu-Mg原子团簇及δ'相在人工时效早期溶解，导致硬度下降；随后大量的GPB区弥散均匀析出，硬度回升，随时效时间延长T₁相析出，硬度进一步增加，在96 h出现第一个强化峰；随后，GPB区溶解，合金硬度降低；继续延长时效时间，T₁相体积分数及板条状S相的数量增加，合金硬度再次升高，在192 h出现第二个强化峰。研究表明自然时效原子团簇可明显改变合金的人工时效析出行为及力学性能演变规律。

Due to their excellent combination of low density, high strength, and stiffness, third-generation Al-Cu-Li-Mg alloys are important lightweight materials in the aerospace industry. Precipitation strengthening or hardening, which is controlled by precipitates, including the structure, size, morphology, distribution, and volume fraction of precipitates, is mainly responsible for the alloy's excellent mechanical properties. The precipitates in Al-Cu-Li-Mg alloys mainly include T₁, S, δ', δ'/θ'/δ', θ', GPB, and various metastable phases. In practice, the Al alloys are inevitably stored for a period at ambient temperature before subsequent processing during which natural aging occurs. Natural aging has an important effect on the precipitation behavior of subsequent artificial aging in Al-Cu-Li-Mg alloys, but the related mechanism is still highly controversial. To solve this problem, the effects of natural aging treatment on the microstructure and mechanical properties of an Al-2.95Cu-1.55Li-0.57Mg-0.18Zr alloy treated by artificial aging at 160^oC were investigated using TEM, three-dimensional atom probe (3DAP), three-dimensional electron tomography (3DET), and mechanical property testing. It was discovered that natural aging significantly changed the artificial aging hardening behavior and caused two strengthening peaks in the alloy's hardness curve. The Mg-rich and Cu-Mg clusters and δ' precipitates formed during natural aging were first dissolved at the initial stage of artificial aging, which resulted in a decrease in hardness. Then, large numbers of GPB zones formed uniformly and dispersedly, followed by the formation of T₁ precipitates with the increase of aging time, which caused the increase in hardness. The hardness reached its first peak value at 96 h. Following that, GPB zones dissolved and the hardness decreased again. When the aging time was continuously exceeded, the volume fraction of T₁ precipitates and the number of lath-like S precipitates increased, so the hardness increased again and reached the second peak value at 192 h. In other words, the atomic clusters that form during natural aging can significantly modify precipitation behaviors and the evolution of mechanical properties during artificial aging.