The effect of quenching rate on strengthening behavior of an Al-Zn-Mg-Cu alloy 7085 during natural ageing has been investigated by hardness, tensile testing, differential scanning calorimetry, transmission electron microscopy, high resolution transmission electron microscopy and three dimensional atom probe. Quench-induced Y phase forms in the air-cooled condition and contributes a remarkable 100 MPa to the as-quenched strength. The air-cooled condition continues to exhibit higher hardness and strength than for the rapid, water-cooled condition during natural ageing for up to about 30000 h. With the increase of natural ageing time, the hardness difference tends to decrease slowly within the first 0.5 h, then sharply until about 20 h, and finally approaches a constant, small difference. The reasons for this unusual quench sensitivity are discussed based on the different precipitation features arising during quenching and natural ageing.

通过硬度，拉伸试验，差示扫描量热法，透射电子显微镜，高分辨率透射电子显微镜和三维原子探针研究了淬火速率对Al-Zn-Mg-Cu合金7085的自然时效强化行为的影响。淬火诱发的Y相在空冷条件下形成，并为淬火后的强度贡献了惊人的100 MPa。在自然老化过程中长达约30000 h时，风冷状态比快速水冷状态继续显示出更高的硬度和强度。随着自然时效时间的增加，硬度差趋于在最初的0.5 h内缓慢降低，然后急剧下降直至约20 h，最后接近恒定的小差值。