断续时效对7050铝合金强度和断裂韧性的影响

Effects of interrupt aging on strength and fracture toughness of 7050 aluminum alloy

采用光学显微镜、扫描电镜、透射电镜、常温拉伸及断裂韧性实验,研究断续时效对7050铝合金力学性能和断裂韧性的影响。研究结果表明:延长二级时效时间,合金强度先增大后减小,断裂韧性先减小后增大;在二级时效过程中,晶内发生了二次析出,小析出相对基体产生了额外的强化作用,使断续时效态合金强度比峰值时效态(T6)合金的强度更高;晶界析出相粗化不连续分布,使断裂韧性比T6态合金的更大;随着二级时效时间的延长,断裂方式由穿晶剪切断裂经沿晶断裂变为穿晶韧窝断裂。

The effects of the interrupt aging on the tensile property and fracture toughness of 7050 aluminum alloy were investigated by optical microscopy,scanning electron microscopy,transmission electron microscopy,tensile and toughness tests.The results show that with the increase of the secondary aging time,the strength of the interrupt aged alloys first increases and then decreases.Meanwhile,the fracture toughness first increases and then decreases.Secondary precipitation takes place in the low temperature aging process,which results in higher strength than that of the peak aged alloy.With the increase of the secondary aging time,the precipitates at grain boundaries of the interrupt aged alloy become coarser and discontinuous,which leads to higher fracture toughness than that of the peak aged alloy.The main fracture mechanism changes from shear transgranular fracture to intergranular fracture,and then to transgranular fracture.