Phase transformation behavior of Ti-1023 under static heat treatment and dynamic thermo-mechanical coupling

The phase transformation of a near-p titanium alloy is extremely sensitive to the processing technique, which significantly affects its mechanical characteristics. The spherical a phase increases the plasticity of a beta titanium alloy, whereas its needle-like a phase prevents dislocations and increases the alloy strength. In this study, we investigate the microstructural evolution and orientation relationship of Ti-1023 alloy under static heat treatment and dynamic thermo-mechanical coupling at 750 degrees C. The results indicate that under the thermo-mechanical coupling conditions, the spherical a phase precipitates at grain boundaries and low-angle grain boundaries, and its volume fraction increases from 10.5% to 23.2% as the strain rate decreases. The Burgers orientation relationship (BOR) between the alpha/beta phases is gradually disrupted as the strain rate increases. On heat treatment, the alpha phase at the grain boundaries becomes discontinuous in a strip-like shape, whereas that within the grain appears needle-like. The grain-boundary a phase becomes more continuous as the heat treatment duration is extended, and the alpha phase gradually broadens. Moreover, the precipitated alpha more tends to obey the BOR. These results could provide important reference for the regulation of the microstructure of a near-beta titanium alloy and the optimization of the process parameters of its deformation heat treatment.

Automated summary

The microstructural evolution and orientation relationship of Ti-1023 alloy under static heat treatment and dynamic thermo-mechanical coupling at 750 degrees C were investigated. The results showed that under the thermo-mechanical coupling conditions, the spherical a phase precipitated at grain boundaries and low-angle grain boundaries, increasing its volume fraction. On heat treatment, the alpha phase at the grain boundaries became discontinuous in a strip-like shape, while within the grain it appeared needle-like. The grain-boundary a phase became more continuous as the heat treatment duration was extended.