不同应力下7B04 铝合金的疲劳断口 - 中南大学学报.PDF

41 1 () Vol.41 No.1 2010 2 Journal of Central South University (Science and Technology) Feb. 2010 7B04 ( 410083) 285 MPa 250 µm 430 MPa 45˚ TG166.3 TG111.8 A 1672−7207(2010)01−0132−06 Fatigue fracture of 7B04 aluminum alloy under different stresses JIAN Hai-gen, JIANG Feng, WEN Kang, HUANG Hong-feng, WEI Li-li, JIANG Long (School of Materials Science and Engineering, Central South University, Changsha 410083, China) Abstract: The microstructures of fatigue fracture of Al alloys under various stresses were studied by optical microscope and scanning electron microscope, and the microscopic features of crack initiation and propagation in this kind of alloy were revealed. The results show that the fatigue cracks usually initiate at or near the free surfaces of the specimen. And with the increase of the loading stress, the distance between the crack and the surface decreases. The cracks are 250 µm in depth from the surface under strain of 285 MPa, while they are initiated at the free surface under 430 MPa. Striation can’t be observed in the area near the crack source. Moreover, the area will be reduced with the increase of loading stress. In the crack propagation zone, there is a uniform increase in striation distance as the strain amplitude increases. After the formation of cracks, the micro cracks propagate towards the depth along the direction of maximum shear stress at an angle