Dynamic recrystallization and texture evolution of Ti-22Al-25Nb alloy during plane-strain compression

To investigate the dynamic recrystallization (DRX) mechanism and texture evolution of Ti-22Al-25Nb alloy during the thermal mechanical processing, plane-strain compression tests were carried out on Gleeble-3500 thermo-mechanical simulator with various strains of 0.36, 0.70 and 1.20, respectively. The results show that the microstructures are significantly sensitive to strains. With the increasing strain, the increased deformation storage energy provides larger driving force for the movement of dislocation and the migration of boundaries, leading to a distinct increase of DRX degree. The nucleation and growth of DRX grains will cause the rearrangement and annihilation of mobile dislocation, as well as the increase of fLAGBs. Particularly, the evolution of dislocation substructures can be identified as: high density dislocation→subgrain→DRX grain. DRX is the dominant softening mechanism for this studied alloy, including the continuous dynamic recrystallization (CDRX) characterized by the transformation of the low angle grain boundaries (LAGBs) to the high angle grain boundaries (HAGBs), and the discontinuous dynamic recrystallization (DDRX) characterized by the grain boundary bulging. Meanwhile, the DRX behavior exhibits an obvious weakening effect on the deformation textures due to the random orientations of DRX grains.