Microstructure and notched high-cycle fatigue property of laser melting deposited TC18 titanium alloy

Microstructure and high-cycle fatigue property of notched specimens of laser melting deposited (LMD) TC18 titanium alloy were investigated. The results show that as-deposited microstructure consists of directional short column grains and equiaxial grains, with extremely fine basket-weave microstructure. After double-annealing treatment, coarse lamellar-like basket-weave microstructure was obtained. With the increasing of maximum cyclic stress, the length of main crack and fatigue life decreased. The SEM micrographs indicate that the notched fatigue crack source of LMD TC18 titanium alloy was alone and initiated at the surface of the notch root. Two types of secondary cracks were detected at the fatigue crack propagation zone. The secondary cracks help consume energy and improve the fatigue strength.