真空环境下欠时效态2A12合金的疲劳行为

在低温真空拉-压疲劳试验机上对欠时效态2A12合金的疲劳行为进行了研究,并采用扫描电镜(SEM)分析了真空环境对疲劳断口形貌的影响.结果表明,真空环境使疲劳寿命提高,疲劳曲线右移.在低循环应力时,真空环境中的疲劳断裂次数可比室温大气环境中的多一个数量级.真空和室温大气环境下的疲劳断口均为穿晶断口.在室温大气疲劳断口上可观察到轮胎花样与疲劳条纹.疲劳条纹在低循环应力时出现疲劳条纹的区域增多,真空环境下极少出现轮胎花样与疲劳条纹.文中对真空环境影响欠时效态2A12合金疲劳行为的原因进行了讨论.

Fatigue behavior of underaged 2A12 alloy in Vacuum

The fatigue behaviors of underaged 2A12 alloy in air and vacuum at room temperature were investigated using a tension-compresion fatigue testing machine. The effect of vacuum on the fatigue behavior was studied by means of Scanning Electron Microscopy (SEM). The results showed that, the fatigue life was noticeably improved in vacuum than that in air, and the S-N curve shifted to the right in vacuum. Under lower cyclic stresses, the fatigue cycles to failure in vacuum was increased an order of magnitude. Both the fractures in air and vacuum were transgranular. Tyre-like patterns and fatigue striations were observed in some local areas of fatigue fractures in air, and more areas with the fatigue striations existed under lower cyclic stresses. However, little fatigue striations existed and tyre-like patterns in vacuum. The reason for the effect of vacuum on the fatigue behavior of underaged 2A12 alloy was discussed.