2A12铝合金动态腐蚀-疲劳耦合失效机理研究

目的 针对某飞机吊挂结构用2A12铝合金开展预腐蚀后的动态腐蚀-疲劳耦合试验,很快发生断裂行为,寻找失效原因并提出解决措施.方法 利用自制的卧式动态腐蚀-疲劳试验装置,开展2A12铝合金预腐蚀后的腐蚀-疲劳协同试验直至样品断裂.同时,对比开展2A12铝合金腐蚀与疲劳交替试验,分析断口腐蚀形貌、元素含量、价态变化,获得2A12铝合金在两种试验方法下的腐蚀疲劳机理.结果 2A12铝合金主要由铝基体以及弥散分布其中的多种合金强化相组成.当有预裂纹时,2A12铝合金在腐蚀与疲劳交替作用下,很快发生疲劳断裂,且裂纹几乎贯穿整个断面,在整个裂纹附近存在较多的腐蚀产物Al2O3.2A12铝合金在预腐蚀后,基体与其表面的氧化膜之间形成腐蚀电池,初期的点蚀孔快速发展成明显腐蚀坑并产生大量腐蚀产物Al2O3,腐蚀坑底部由于应力集中现象而成为裂纹源,在动态腐蚀-疲劳耦合作用下快速萌生裂纹并呈放射状扩展,很快发生疲劳断裂行为,同时裂纹扩展区无腐蚀产物.结论 2A12铝合金用作飞机吊挂结构件时,必须进行表面防腐处理,避免形成腐蚀坑,减缓吊挂结构发生腐蚀-疲劳断裂进程.

Study on Dynamic Corrosion-Fatigue Coupling Failure Mechanical of 2A12 Aluminum Alloy

2A12 aluminum alloy used for a suspension structure of an aircraft adopts a dynamic corrosion-fatigue coupling test after pre-corrosion, and the fracture behavior soon occurs. It was necessary to find the failure reason and propose solutions. Using the self-made horizontal dynamic corrosion-fatigue test device, carry out the corrosion fatigue test after the 2A12 aluminum alloy pre-corrosion until the sample breaks. At the same time, 2A12 aluminum alloy corrosion and fatigue alternate test were carried out to analyze the fracture corrosion morphology, element content, and valence changes. Corrosion fatigue mechanism of 2A12 aluminum alloy was obtained under two test conditions. 2A12 aluminum alloy was composed of an aluminum matrix and a variety of dispersed alloy strengthening phases. When there was a pre-crack, the 2A12 aluminum alloy would quickly undergo fatigue fracture under the alternate action of corrosion fatigue, and the crack almost penetrated the entire section, and there were many corrosion products near the crack, aluminum oxide. After 2A12 aluminum alloy was pre-corroded, a corrosion cell was formed between the substrate and the oxide film on its surface. The initial pitting corrosion pitted and produced a large number of corrosion products. The bottom of the corrosion pit became the source of cracks due to stress concentration. Under the synergistic effect of corrosion fatigue, cracks were gradually initiated and expanded radially, fatigue fracture behavior occurred quickly, and there was no corrosion product at the crack propagation zone. Therefore, when 2A12 aluminum alloy was used as an aircraft suspension structure, the surface must be treated with anti-corrosion to avoid the formation of corrosion pits, and then slow down corrosion fatigue fracture process.