The Fatigue Behavior of TC4 and Ti60 Dissimilar Titanium Alloy Joints Welded by Electron Beam

During use, titanium alloy structural components may experience sudden overloads or occasional loads, which can reduce their fatigue life and accelerate structural failure. To study the fatigue behavior of TC4/Ti60 joints, this paper uses electron beam welding technology to obtain TC4/Ti60 dissimilar joints. The results show that the microstructure changes during the welding process, with the weld zone being relatively uniform, primarily consisting of coarse α′ phase. The near heat-affected zone on the TC4 side consists of α′, while on the Ti60 side, in addition to the α′ phase, there is a small amount of residual α phase. Fatigue tests reveal that as the pre-deformation increases, the fatigue life gradually decreases. During the early stages of fatigue, the joint exhibits cyclic hardening, which transitions to cyclic softening as the test progresses, ultimately leading to failure. Fatigue fracture analysis reveals that all fatigue samples failed on the TC4 side, with no failure observed in the weld zone. This is likely due to the presence of martensite, which gives the weld zone higher strength than the TC4 base materials. Additionally, fatigue cracks initiated from surface or near-surface defects, with ductile fractures being predominant.