Research on microstructure and high-temperature properties of Ti17 titanium alloy fabricated by laser solid forming

The sample fabricated by laser solid forming (LSF) consists of laser repaired zone (RZ), heat affected zone (HAZ) and forge substrate. The repaired zone consists of coarse columnar β grains which grow epitaxially from the substrate. And β grains are made of extremely fine basket-weave microstructure where a lot of fine acicular α phases precipitate on. Microstructure of heat affected zone transits from duplex microstructure to basket-weave microstructure. After 600°C, 1 h furnace cooling annealing continuity of columnar, β grain boundaries have not been affected, and α laths grow slightly and length/width ratio of α laths decreases. Microhardness test shows that hardness value of annealed sample is 5% higher than that of as-deposited sample. The results of high temperature tensile properties and high cycle fatigue property of annealed samples suggest that compared with the forging standard, the tensile strength index is higher while ductility index corresponds to the standard. The fatigue limit is 295 MPa which reaches 70% of the forging standard. At last, failure behavior and fracture mechanism of laser repair samples under different loading modes are analyzed.