针对自然时效使Al-Zn-Mg-Cu合金峰值时效强度出现矛盾响应的现象，本工作以新型超高强铝合金Al-9.8Zn-2.23Mg-1.38Cu-0.11Cr-0.1Zr (质量分数，%)为研究对象，通过高角度环形暗场扫描透射电子显微技术和三维原子探针断层扫描技术，系统探究了自然时效时间对峰时效状态下析出相演化、溶质元素分布及力学性能的调控规律。结果表明，自然时效会加速后续人工峰值时效的响应速度。自然时效处理0、1、7和30 d后，经人工时效获得的峰值强度分别为(708 ± 4)、(685 ± 3)、(712 ± 1)和(722 ± 1) MPa，随自然时效时间延长呈现先降低后升高的趋势。这是由于短时自然时效形成的GPI区会在人工时效处理阶段部分溶解，降低后续GPI区、GPII区和η′相的数密度并促进相长大。而自然时效时间的延长使尺寸大于临界形核尺寸的GPI区比例增大，有助于在后续峰值时效时获得更为细小、弥散的析出相，也使得峰值时效下的GPII区比例逐渐增大、η′相比例逐渐降低。

Al-Zn-Mg-Cu alloys are widely used to prepare aerospace lightweight structures owing to their excellent specific strength and damage tolerance. Their performance depends mainly on the high-density nanoprecipitates formed during artificial aging. However, natural aging after solution quenching changes the evolution path of the precipitates, affecting the subsequent artificial aging process. Currently, there is still considerable controversy regarding the impact of natural aging on the peak strength of these alloys after artificial aging. Therefore, this study investigated the contradictory effects of natural aging on the peak-aged strength of Al-Zn-Mg-Cu alloys after artificial aging. Using a newly developed ultrahigh-strength aluminum alloy, namely Al-9.8Zn-2.23Mg-1.38Cu-0.11Cr-0.1Zr (mass fraction, %), the effects of natural aging on precipitate evolution, solute element distribution, and mechanical properties in the peak-aged state were systematically explored. The results showed that natural aging accelerated the response of the material to subsequent artificial aging. The peak strengths after 0, 1, 7, and 30 d of natural aging and artificial aging were (708 ± 4), (685 ± 3), (712 ± 1), and (722 ± 1) MPa, respectively, exhibiting a trend of initial decrease followed by an increase. This behavior was attributed to the formation of Guinier-Preston I (GPI) zones (1.1-1.7 nm in diameter) during short-term natural aging (1 d), which partially dissolved during artificial aging. This reduced the number density of subsequently formed GPI zones, Guinier-Preston II (GPII) zones, and η′ phases and promoted their coarsening. In contrast, prolonged natural aging time increased the proportion of GPI zones, with sizes exceeding the critical nucleation threshold at artificial aging temperatures, facilitating the formation of finer and more dispersed precipitates during subsequent peak aging. Further, this led to a gradual increase in the proportion of GPII zones and decrease in the proportion of the η′ phase. Compared to the peak-aged sample naturally aged for 1 d, the sample naturally aged for 30 d exhibited an approximately 20% increase in the precipitate number density. In addition, the compositional gradient within precipitates of similar size became less pronounced, with significantly reduced maximum concentrations of Zn, Mg, and Cu.