The influence of hot rolling deformation on recrystallization and texture evolution of Ti551 alloy

As a representative thermomechanical processing step, hot rolling can generate texture evolution that is critical to the strength–ductility synergy of titanium alloys. Ti551 is a newly developed medium-strength, high-toughness alloy designed for deep-sea service; however, its texture-evolution behavior during rolling remains unclear. In this work, Ti551 as-forged billets were hot rolled at near β-transus temperature region (T_β, 950 ℃) with reductions from 5% to 50%. Electron backscatter diffraction (EBSD) was used to quantitatively analyze the fractions of low-angle grain boundaries (LAGBs), grain orientation spread (GOS) and the evolution of α {0001} texture. The results show that, taking the annealed condition (0 reduction) as the reference, when the cumulative reduction increases from 0 to 30%, the area fraction of recrystallized/strain-relieved regions decreases from ~55% to ~36%, and remains nearly unchanged as the reduction is further increased to 50%. In addition, hot rolling develops a basal texture, but its overall intensity decreases with increasing reduction (i.e., the peak intensity drops and the texture becomes more diffuse). These finds indicate that under near T_β condition, when the rolling direction is perpendicular to the dominant texture direction of the forged billet, a higher cumulative reduction is more effective in weakening the basal texture and dispersing the orientation peaks. This can help select the final-pass reduction to obtain a basketweave microstructure with smaller orientation-cluster length scales and improved microstructural uniformity.