Microstructure and mechanical properties of laser-deposited Ti65 near-alpha titanium alloy

Ti65 titanium alloy samples were fabricated by laser deposition manufacturing (LDM) technology, and defects, microstructures and mechanical properties of the LDMed Ti65 samples were investigated. Results showed that there were pores and lack of fusion defects in the sample deposited with low-power laser, and an obvious crack appeared at the bottom of the sample. While in the sample deposited with high-power laser, the pores were much smaller and no other detected defects. After annealing, the defects of these samples did not change markedly. Widmanstatten microstructure was exhibited and no strengthening phases were precipitated in the low-power laser-deposited sample. Lamellar microstructure was exhibited, and Ti3Sn strengthening phases and tungsten-rich phases were presented in the high-power laser-deposited sample. After annealing, both of them changed to basketweave microstructures, but alpha lamellas of the high-power laser-deposited sample were coarsened more notably. The average strength and plasticity of the high-power laser-deposited sample were higher than those of the low-power laser-deposited sample by 6 MPa and 1.4%, respectively. After annealing, strength and plasticity of these samples were improved, and the average strength and plasticity of the high-power samples were still higher than those of the low-power samples by 22 MPa and 3.9%, respectively. The microhardnesses of the as-deposited and annealed samples deposited with high-power laser were greater than those of the corresponding samples deposited with low-power laser.