(1. 江苏工业学院 材料科学与工程学院，常州 213164；2. 中南大学 材料科学与工程学院，长沙 410083)
摘 要: 测试等屈服强度条件下190 ℃，1 h欠时效和190 ℃，46 h过时效状态Al-Cu-Mg系2E12铝合金的疲劳寿命，并分别采用扫描电镜和透射电镜观察了疲劳断口形貌及时效析出特征，并在此基础上解释时效析出对2E12铝合金疲劳断裂行为的影响。结果表明：疲劳裂纹主要萌生于试样表面的粗大残留相位置；由于过时效试样晶内析出大量的S平衡相降低疲劳变形时的位错滑移可逆性，加剧晶界处位错塞积程度；同时晶界上较宽的无析出带和沿晶界析出的粗大针状S相进一步促进晶界集中变形和开裂，从而降低过时效试样的疲劳寿命。
关键字: 铝合金；疲劳断裂行为；时效析出
（1. School of Materials Science and Engineering, Jiangsu Polytechnic University, Changzhou 213163, China;2. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract: The fatigue lives of Al-Cu-Mg based 2E12 aluminum alloy under 190 ℃, 1 h and 190 ℃, 46 h were measured. The fractographies and the characteristics of ageing precipitation were investigated using scanning electron microscopy and transmission electron microscopy, respectively. The results show that the fatigue cracks are initiated around the coarse secondary phases on the free surfaces of the specimens. After over-ageing treatment, the equilibrium S phases precipitate the reversible movement of dislocations and further intensify their piles-up on the grain boundaries. On the other hand, the presence of wider PFZs and needle-shaped S phases on grain boundaries accelerate the localized deformation within PFZs and fast cracking along the grain boundary S phases. Therefore, the fatigue properties of the overaged specimens are deteriorated compared with that of the under-ageing specimens.
Key words: aluminum alloy; fatigue fracture behavior; ageing precipitation
