【摘要】 分别熔炼了含Li和不含Li的2种7XXX系合金,合金经过双级时效（120℃+160℃）后,利用TEM研究了第二级时效峰值状态时的微观组织。结果表明,2种合金的沉淀强化相均是η′（MgZn₂）。与不含Li合金相比,含Li合金具有更细小的析出强化相和更窄的沉淀无析出带（PFZs）。更多还原

【Abstract】 Two kinds of Al-Zn-Mg-Cu based alloys with and without Li addition were prepared by ingot metallurgy. The specimens were undertaken by a two-steps aging after solid solution quenching, namely at 120℃ for 3 h followed by 160℃ for different hours. The mi-crostructures of peak-aged specimen during the second step aging were examined by transmission electron microscopy (TEM) . The results showed that the precipitates with hardness peak for both alloys were normally η’’ phase (MgZn2). However, by contrast with the Li-free alloy, the precipitation phases were much fine in dimension, and the precipitation free zones (PFZs) were much narrow for the Li-adding alloy. The reason could be probably attributed to the role of Li trapping vacancies, as a consequence, the diffusion of Zn and Mg atoms was restrained, then, the growth of η’ phase was slowed down. The results were discussed with a theory of aging kinetics.更多还原