Low cyclic fatigue behavior of electron-beam-welded Ti–6Al–4V titanium joint

The low cycle fatigue (LCF) tests were carried out using symmetrical cyclic loading under total strain amplitude control conditions. The present paper is devoted to investigating the cyclic deformation response of Ti–6Al–4V titanium and the electron-beam-welded (EBW) joint in the following aspects, i.e., cyclic deformation behavior, fatigue life and fatigue fracture behavior. The results show that the softening of the joint is significant at larger strain ranges, while not obvious at smaller strain ranges. The joint shows shorter fatigue life at larger strain ranges and equivalent fatigue life at smaller strain ranges compared with Ti–6Al–4V base metal. A fatigue crack of the joint not only originates at the surface or subsurface, but also at defects in the fusion zone (FZ). The crack propagation zone of Ti–6Al–4V base metal shows ductile fracture mechanism, while the joint shows brittle fracture mechanism. In all the fatigue fracture zones many dimples appear, showing the typical ductile fracture.