Effect of subphase change point temperature cyclic heat treatment on the microstructure and mechanical properties of Ti65 high-temperature titanium alloy fabricated by laser deposition manufacturing

Laser deposition manufacturing(LDM) offers a novel approach for the fabrication of Ti65 high temperature titanium alloy components. However, the plasticity of Ti65 components manufactured via laser deposition is relatively low. To enhance the comprehensive mechanical properties of additively manufactured Ti65 titanium alloy components, heat treatment is employed to regulate strength and toughness. Nevertheless, the underlying mechanisms by which the heat treatment system influences the microstructure, precipitates, and mechanical properties of these components remain unclear. In this study, LDM Ti65-alloy components are subjected to subphase change point cyclic-heat-treatment and subphase change point temperature solution heat treatment. The mechanisms of different heat treatment regime on the microstructure, precipitates, and mechanical properties for LDM Ti65 components are systematically investigated. Research findings indicate that when cyclic-heat-treatment is combined with solution treatment, the alloy microstructures undergo substantial modifications. The α GB become discontinuous, the α-laths coarsen, and fine α phases precipitate. In additionally, silicates at the phase boundaries completely vanish. During the room-temperature tensile testing, the sample exhibits an 8.78% increase in horizontal plasticity and an 11.56% increase in vertical plasticity, accompanied by minimal strength loss. Consequently, the comprehensive mechanical properties of the material are significantly enhanced. This study demonstrates that the optimal heat treatment process is 1030°CCHT/FC+1020°C/2h/AC. The changes in microstructure morphology after heat treatment and the disappearance of silicates enhance the plasticity of the components, and the precipitation of α s ensures that the strength of the components does not significantly decrease.