中文摘要：

基于回归再时效（RRA）工艺,提出一种新的回归-应力时效制度（RSA）用于Al-Zn-Mg-Cu合金。系统研究了应力时效制度（时效时间和应力）对回归态Al-Zn-Mg-Cu合金析出相的影响。透射电镜（TEM）观察结果表明：在回归处理后,合金内部存在大量的基体析出相（MPts）和轻微不连续的晶界析出相（GBPsi时效时间和应力对回归态合金析出相的影响十分显著。随着时间和应力的增加,基体析出相的尺寸增加而密度减少;同时,晶界析出相的尺寸、间距和无沉淀的宽度也增加。相比于回归再时效工艺,回归-应力时效工艺使得晶内析出相尺寸增加,无沉淀析出带变窄且晶界析出相更不连续。

英文摘要：

According to retrogression and re-aging treatment（RRA）,a novel retrogression and stress-aging treatment（RSA） was put forward for Al-Zn-Mg-Cu alloys.The effect of stress-aging time and external stress on precipitates of pre-retrogressed Al-Zn-Mg-Cu alloy was investigated by transmission electron microscope（TEM）.The observation shows that there is a large number of matrix precipitates（MPts） and slightly discontinuous grain boundary precipitates（GBPs） in the pre-retrogressed alloy.The effects of stress-aging time and external stress on precipitates of the retrogressed alloy are significant.With the increase of stress-aging time and external stress,the size of MPts increases and the density of MPts decreases.Meanwhile,the size of GBPs,the distance between GBPs and the width of precipitate free zone（PFZ） increase.Compared with the traditional retrogression and re-aging treatment,the retrogression and stress-aging treatments increase the size of MPts,narrows the width of PFZ and make the GBPs more discontinuous for the studied Al-Zn-Mg-Cu alloy.