Dynamic recrystallization and hot processing map of Ti-48Al-2Cr-2Nb alloy during the hot deformation

Dynamic recrystallization (DRX) mechanism of Ti-48Al-2Cr-2Nb (at. %) alloy was investigated by thermal uniaxial compression experiments in this work. The deformed microstructure showed that in addition to the discontinuous dynamic recrystallization (DDRX) with the typical feature of grain nucleation and growth, continuous dynamic recrystallization (CDRX) charactered by the crystal orientation accumulation also appeared in γ grains during the hot compression at 1200 °C/0.01 s⁻¹. The crystal orientations of CDRX grains were nearly close to the 〈001〉 orientation at the strain of 0.92. Also, the emergence of DRX in the γ laths of lamellar colonies was confirmed by microstructure characterization, and the α₂ → γ phase transformation occurred simultaneously. On the other hand, the GOS threshold value for distinguishing the deformed grains and DRX grains was analyzed to quantitatively calculate the DRX volume fractions. A novel hot processing map with the strain of 0.92 based on the DRX volume fraction was established to obtain the deformation parameters for the full DRX and provide the theoretical results for optimizing the thermo-mechanical treatment of TiAl alloy (approximately 1100 °C/0.001 s⁻¹ and 1200 °C/0.01 s⁻¹).