Synergistic Effect of Strain Accumulation and Isothermal Holding Time on Spheroidization and Recrystallization of Ti–6Al–2Sn–4Zr–6Mo Alloy During Hot Compression Deformation

In this study, the effects of cumulative deformation and holding time on the rheological softening behavior, microstructure evolution, and phase transition mechanisms of Ti–6Al–2Sn–4Zr–6Mo alloy under thermal‐mechanical coupling conditions were investigated. The findings indicate that the steady‐state stress of single‐pass hot compression is the highest; meanwhile, stress gradually decreases with the increasing deformation passes during multi‐pass deformation. This softening phenomenon is attributed to a shift in the dominant restoration mechanism: single‐pass deformation is primarily governed by dynamic recrystallization, whereas multi‐pass compression induces α → β → α phase transformation. Initially, the fraction of α phase decreases, subsequently increasing during the holding period, while the morphology of α phase transitions from lath to spheroidization. In the course of multi‐pass hot compression, the deformation mechanism transforms from phase transformation‐dominated microstructure to shear‐dominated dynamic spheroidization, reaching a strain of 0.6. Ultimately the microstructure transforms to equiaxed α at a strain of 0.8. Additionally, the newly formed α phase and the parent β phase follow the Burgers orientation relationship. Dislocation density decreases with increasing number of passes, while the α phase, reversely transformed, nucleates along dislocation lines and grows by absorbing dislocations. Texture gradually transforms from the initial basal texture to //RD with increasing total strain.