AA2524-T34铝合金的微观结构与疲劳裂纹萌生机制

The Microstructure and Fatigue Initiation of an AA2524-T34 Aluminum Alloy

通过对新型铝合金AA2524-T34的四点弯曲疲劳实验,结合光学显微镜和电子扫描电镜(SEM),对疲劳试样表面和疲劳断口进行了微观观测,研究了材料的微观结构及在不同相对湿度下材料的疲劳裂纹萌生机制。实验应力比0.1,加载频率15 Hz,实验相对湿度15%和95%。结果显示实验材料呈现了完全再结晶的层状晶粒结构,晶粒沿着轧制方向被拉长,并较为平坦。不同相对湿度下,多数疲劳裂纹萌生于材料中含Fe的粗大的β相粒子,同时伴有少量的滑移带裂纹形核、材料缺陷裂纹形核等;高相对湿度下,可见裂纹沿晶界启裂。

The micro structure and mechanism of fatigue initiation of an AA2524 AI alloy was investigated at the present paper. Four-point bend fatigue tests were conducted on the test alloy along the roiling direction at room temperature and frequency of 15 Hz, R =0.1, in relative humidity 15% and 95% air, combining with optical microscopy and electronic scanning microscopy （SEM） to observe the surface and fracture surface of tested samples. It was found that the flat grain was elongated along the rolling direction, showing the layer grain structure. At different relative humidity, the majority of fatigue cracks were initiated on the coarse β phase second particle, containing Fe, a few of them were formed on sites of material defects or slip bands. At high relative humidity, it could be observed the fatigue crack formed at grain boundary.