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 gamma grains during the hot compression at 1200 degrees 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 gamma laths of lamellar colonies was confirmed by microstructure characterization, and the alpha 2 -* gamma 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 degrees C/0.001 s-1 and 1200 degrees C/0.01 s-1).

Automated summary

The study investigated the dynamic recrystallization mechanism of the Ti-48Al-2Cr-2Nb alloy during thermal uniaxial compression experiments. It was found that both discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) occurred in the gamma grains, with the crystal orientations of CDRX grains close to the (001) orientation at a strain of 0.92. The emergence of DRX in the gamma laths of lamellar colonies and the alpha 2 to gamma phase transformation were confirmed, and a new hot processing map based on DRX volume fraction was established to optimize the thermo-mechanical treatment of the TiAl alloy.