Tensile and fatigue behavior of electron beam welded dissimilar joints of Ti-6Al-4V and IMI834 titanium alloys

The aim of this study was to evaluate the microstructure, hardness, tensile and fatigue properties of electron beam welded dissimilar joints between Ti-6Al-4V and IMI834 (Ti-6Al-5Sn-2Zr-1Mo-0.35Si-1Nd) titanium alloys. A significant microstructural change was observed to occur after welding, with martensite in the fusion zone (FZ) and in the heat-affected zone (HAZ) of Ti-6Al-4V side, and martensite plus some retained α phase in the HAZ of IMI834 side. An asymmetrical hardness profile across the dissimilar joint was obtained in the dissimilar joint with a higher hardness value in the FZ. Fatigue life of the dissimilar joint was nearly the same as that of the BMs. The dissimilar joint exhibited cyclic stabilization at lower strain amplitudes up to 0.6%, while cyclic softening occurred after initial cyclic stabilization at higher strain amplitudes. Fatigue failure of the dissimilar joints occurred in the IMI834 BM, with crack initiation from the specimen surface or near-surface defect and crack propagation characterized by fatigue striations along with secondary cracks.