Materials Science & Engineering
CHEN Li-jia, NING Hao-nan, ZHANG Zhi-peng, ZHANG Yu-peng, ZHOU Ge
In order to determine the fatigue properties of narrow gap TIG welded joint of thick TC4 titanium alloy plate, the high cycle fatigue (HCF) tests at room temperature were carried out with the samples at three layers of welded joint, respectively. The morphologies of fatigue fracture surfaces and the microstructures near the fracture surface were observed and analyzed with scanning electron microscope and transmission electron microscope. The results show that the fatigue limits of three-layer welded joints are 420 MPa, 390 MPa and 400 MPa, respectively. For the first layer of welded joint, the fatigue crack initiation position is the sample surface, and the dislocation configuration is mainly dislocation network and dislocation array. For the second layer of welded joint, the fatigue crack initiation positions are both sample surface and welding defects, and the dislocation configuration is mainly dislocation tangles. For the third layer of welded joint, the fatigue crack initiation positions are sample surface and near-surface welding pores, and the dislocation configuration is mainly dislocation array and tangles.