Evolution behavior of precipitated phases and performance stability of TA37 titanium alloy during thermal exposure

: This research systematically explored the evolution rules of precipitated phases in the TA37 near-α titanium alloy during long-term thermal exposure at 600 °C (ranging from 100 to 1000 hours) and their impacts on the properties. Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and diffraction analyses indicated that after thermal exposure, the α 2 phase precipitated dispersively within the α phase. It exhibited a complete coherent relationship with the α matrix. The size of the α 2 phase increased as the thermal exposure time extended. Specifically, it grew from 3.7nm at 100h to 7.82nm at 1000h. However, its growth rate gradually decelerated, following the Ostwald ripening kinetics. Simultaneously, silicides, mainly (Ti, Zr) 6 Si 3 , preferentially precipitated at the grain boundaries, dislocations, and residual β phase regions, forming non-coherent interfaces with the matrix. The size of the silicides increased from 35nm at 100h to 98nm at 1000 h. Their coarsening behavior was also diffusion-controlled and tended to stabilize in the later stage due to the depletion of Si atoms. The precipitations have a significant impact on mechanical properties. Precipitated phases exhibit a strengthening effect only within a specific range. The strength declines as the size and volume fraction of α 2 phases and silicides increase beyond this range. In contrast, ductility shows a monotonic decreasing trend with the precipitation of α 2 phases and silicides. The coherent strain of the α 2 phase and the interface characteristics of the silicides together determined the microstructural stability and property change rules of the TA37 alloy. The above-mentioned evolution rules of precipitated phases provide crucial theoretical foundations for the optimization of applications of the TA37 alloy.