Hot deformation behavior and microstructure evolution mechanism of Ti–43Al–4Mo–0.6Mn–0.2C–0.2B alloy

Wrought TiAl alloys are considered as promising high-temperature lightweight structural materials. In this study, isothermal hot compression tests were conducted on a newly developed Ti–43Al–4Mo–0.6Mn–0.2C–0.2B (at.%) alloy. The results show that the flow stress decreases significantly with increasing deformation temperature and decreasing strain rate, exhibiting typical dynamic softening behavior. A constitutive equation based on the Arrhenius-type hyperbolic sine model was established, which accurately predicts the flow stress, yielding a calculated hot deformation activation energy of 616.19 kJ/mol. The optimal hot working window determined from the processing map is in the temperature range of 1150–1200 °C with a strain rate of 0.01 s⁻¹. Microstructure analysis reveals that pronounced dynamic recrystallization (DRX) occurs during hot deformation, resulting in the fragmentation of the initial cast lamellar structure into fine equiaxed grains. At high strain rates, the α₂ phase content abnormally increases. EBSD analyses attribute this to adiabatic‑heating‑induced γ → α₂ phase transformation. This study provides a theoretical basis for the design of hot working processes for TiAl alloys.