中文摘要：

利用洛氏硬度计、电子拉伸试验机、冲击试验机、扫描电镜（SEM）、能谱仪（EDS）等设备对7075铝合金超长时间时效行为、力学性能、抗应力腐蚀性（SCR）及断口形貌进行了研究。结果表明，7075铝合金的硬度及强度都具有时效双峰特征。两个时效峰的硬度和强度相差不多，但对应第二峰时效的合金具有比较高的SCR性能。首次提出并运用“相变-Mg-H”复合理论解释了7075合金第二峰的高SCR性能现象。

英文摘要：

The aging behavior, mechanical properties, stress corrosion resistance properties and microstructure of 7075 aluminum alloys with overlength aging were studied by means of Rochwell hardometer, electronic tensile machine, impact testing machine, scanning electron microscopy （SEM） and energy dispersive X-ray spectrometer （EDS）. The results show that the hardness, strength properties all has double peaks. Although the hardness and strength of two peaks is almost equal, the stress corrosion resistance properties of the alloy at the second ageing peak are higher than those at the first ageing peak. A ＂phase-ehanging-Mg-H＂ theory is put forward firstly, and the mechanics of high-SCR for 7075 alloy second-peaking aged is explained properly by it.