通过疲劳裂纹扩展速率试验和扫描电镜观察研究了T7951二次时效对室温空气环境下7055铝合金疲劳裂纹扩展行为的影响。结果表明: 经二次时效处理后, 该铝合金的裂纹扩展速率有所降低; 二次时效前后铝合金疲劳断口的裂纹稳定扩展区均为准解理断裂, 且均出现平行的疲劳条纹; 二次时效前铝合金出现二次裂纹, 其疲劳条纹间距大于二次时效后的; 二次时效前后铝合金疲劳断口的瞬断区均为韧窝型穿晶断裂。
The effects of secondary ageing of T7951 on fatigue crack propagation behavior of 7055 aluminum alloy at room temperature in the air were investigated through the crack propagation rate test and SEM observation. Results show that the fatigue crack propagation rate of the alloy decreased after secondary ageing. The stable crack propagation areas in fatigue fracture of the aluminum alloy before and after secondary ageing all exhibited quasi-cleavage fracture, and parallel fatigue striations were observed in the above areas. Secondard cracks occured in the aluminum alloy before secondary ageing, and the distance between fatigue striations before secondary ageing was bigger than that after secondary ageing. Transgranular dimple fracture were observed in the final fracture areas in fatigue fracture of the aluminum alloy before and after secondary ageing.