(1. 江蘇工業(yè)學(xué)院 材料科學(xué)與工程學(xué)院，常州 213164；2. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長(zhǎng)沙 410083)
摘 要: 測(cè)試等屈服強(qiáng)度條件下190 ℃，1 h欠時(shí)效和190 ℃，46 h過時(shí)效狀態(tài)Al-Cu-Mg系2E12鋁合金的疲勞壽命，并分別采用掃描電鏡和透射電鏡觀察了疲勞斷口形貌及時(shí)效析出特征，并在此基礎(chǔ)上解釋時(shí)效析出對(duì)2E12鋁合金疲勞斷裂行為的影響。結(jié)果表明：疲勞裂紋主要萌生于試樣表面的粗大殘留相位置；由于過時(shí)效試樣晶內(nèi)析出大量的S平衡相降低疲勞變形時(shí)的位錯(cuò)滑移可逆性，加劇晶界處位錯(cuò)塞積程度；同時(shí)晶界上較寬的無(wú)析出帶和沿晶界析出的粗大針狀S相進(jìn)一步促進(jìn)晶界集中變形和開裂，從而降低過時(shí)效試樣的疲勞壽命。
關(guān)鍵字: 鋁合金；疲勞斷裂行為；時(shí)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
