室温大气环境下不同时效态2A12合金的疲劳行为

Fatigue Behavior of 2A12 Alloy at Different Aged States in Air

在拉-压疲劳试验机上对室温大气环境下欠时效态、峰时效态、过时效态和自然时效态2A12合金的疲劳行为进行研究,并采用扫描电镜(SEM)分析室温大气环境下不同时效态对疲劳断口形貌的影响。结果表明:在室温大气环境下,四种时效态2A12合金的疲劳断裂循环次数均随着循环应力的减小而明显增加。循环应力水平越低,疲劳寿命提高越明显;各时效态的疲劳断口均为穿晶断口。断口中均出现疲劳条纹、台阶和韧窝,并在较低循环应力下,疲劳条纹出现的区域较多;欠时效态和峰时效态断口上还可观察到轮胎花样。自然时效态表现出最好的疲劳裂纹扩展阻力,其次是欠时效态、峰时效态,过时效态的疲劳裂纹扩展阻力最低。对室温大气环境下各时效态2A12合金疲劳行为进行了讨论。

The fatigue behavior of under aged, peak-aged,over-aged and nature-aged 2A12 alloy in air at room temperature was investigated using a tension compression fatigue testing machine. The effect of air on the fatigue fractures was studied by means of scanning electron microscopy （SEM）. The results showed that the cycle number of fatigue breakdown increased obviously with the cyclic stress decreasing for each aged 2A12 alloy, the lower the cyclic stress level , the more obvious increased the fatigue lifetime, in atmospheric environment with a room temperature. The fractures of every-aged state in air at room temperature are transgranulars, in which fatigue striations, steps and dimples are observed, and more areas with fatigue striations exist under lower cyclic stresses. Tyre-like patterns are observed on fatigue fractures in air for the under-aged and peak-aged. The best fatigue crack growth resistance is revealed at the natural aging state, then it is decreasing in order of the under-aged ,peakaged state and the over-aged state. The reason for the effect of air on the fatigue behavior of everyaged 2A12 alloy was discussed.