Mechanical properties of electron beam welded dissimilar joints of TC17 and Ti60 alloys

Microstructure, hardness, tensile and high cycle fatigue (HCF) properties of the welded dissimilar joints of Ti60 and TC17 titanium alloys had been investigated in this study. A significant microstructural change was observed to occur after welding, with rod-like α and β phases in the fusion zone (FZ), equiaxed α phases, fine α laths and β phases in the heat-affected zone (HAZ) of TC17 side and acicular martensite α' phases+“ghost” α phases in the HAZ of Ti60 side. The microhardness across the joints exhibited an inhomogeneous distribution with the highest hardness of ∼404 HV in FZ and the lowest hardness of ∼304 HV in base material (BM) of Ti60. All the joints tested in tension fractured at BM of Ti60 side. Fatigue limits of the joints at 107 cycles were 425 MPa at room temperature and 380 MPa at 400 °C, respectively. Welding micropores were found to be the main source of fatigue crack initiation.