Effect of thermal exposure on microstructure and mechanical properties of Ti65 high-temperature titanium alloy deposited by laser direct energy deposition.

Industrial design and new product development benefit from the adaptable processing approach offered by laser direct energy deposition (LDED). In this paper, a novel Ti65 alloy was successfully prepared by LDED and subjected to thermal exposure at 650 °C and 750 °C, respectively. The results showed that the as-deposited microstructure varies in different regions due to the cooling rate. Silicide precipitation was observed at the α/β interface, and a coherent α 2 phase was generated in the matrix after thermal exposure at 650 °C. Two-scale silicides were observed at the α/β interface and inside the α laths after thermal exposure at 750 °C. The as-deposited ultimate tensile strength (UTS) was 1058 MPa and 690 MPa at room temperature and 650 °C, respectively. After thermal exposure at 650 °C, the room temperature UTS was 1135 MPa, and the elongation (EL) at 650 °C was 27.5 %. After thermal exposure at 750 °C, the room temperature EL was 11.05 %, and both UTS and EL at 650 °C showed a decrease. The quantitative analysis showed that silicide precipitation was primarily responsible for the strengthening mechanism of the specimens thermally exposed at 650 °C at room temperature. The results provide scientific data for the manufacture of Ti65 alloy with excellent mechanical properties, laying the foundation for its application in aerospace. • LDED successfully fabricated a novel near-α Ti65 titanium alloy. • Thermal exposure at 750 °C eliminates the α 2 phase coherent with the matrix. • Thermal exposure temperature has a significant effect on the size and morphology of the precipitates. • The influence of microstructure and silicides on the tensile properties was discussed. • As-deposited exhibits an optimal combination of mechanical properties at RT and 650 °C. [ABSTRACT FROM AUTHOR]