Study on microstructure and high cycle fatigue property of laser deposited TA15 titanium alloy

The microstructure of laser deposited TA15 titanium alloy was investigated and high cycle fatigue property including crack initiation and crack propagation at room temperature was analyzed. The fatigue fracture surface and microstructure of longitudinal section were examined by optical microscopy (OM) and scanning electron microscopy(SEM). The results indicate that as-deposited macrostructure consists of directional column grains with extremely fine basket-weave microstructure. After double-annealing treatment, coarse lamellar-like basket-weave microstructure was obtained. The crack initiation region was characterized by crystallographic cleavage facets of lamellar. The crack tended to propagate tortuously, which was related to different orientations of lamellar. Its propagation direction in certain areas was parallel or approximately perpendicular to lamellar and the secondary cracks in the crack propagation region helped consuming energy and improved the fatigue life.