Special deformation mechanisms dominated by grain boundary sliding of extrusion–refined Ti–22Al–25Nb alloy during compression in single BCC phase field

The deformation behavior of Ti–22Al–25Nb alloys with refined initial grain size was investigated under isothermal uniaxial compression in the BCC (B2) single-phase field, where a high-temperature extrusion process was used to produce the test materials with finer initial grains. As compressed at low to moderate strain rates, the present material exhibits significant continuous flow softening. To study the deformation and softening mechanisms during the compression, the samples' microstructures were examined using EBSD. The analysis shows that this alloy has a considerable grain boundary sliding (GBS) mechanism in addition to the conventional mechanisms of dynamic recovery (DRV), dynamic recrystallization (DRX), and texture softening. For the first time, this study offers direct evidence of the presence of GBS in current alloys. And the dominant role of GBS in high-temperature deformation and softening of current alloys was identified by comparing the impacts of various mechanisms on the dislocation density distribution. Besides, the impact of GBS on texture evolution was also discussed.