Comparative Study on Microstructural Evolution and Deformation Mechanisms of a Near‐ α Ti‐551 Alloy and Commercially Pure Titanium During Cryogenic Rolling

Cryogenic rolling is a promising route for achieving superior strength–ductility synergy in titanium alloys, but differences in deformation mechanisms between pure titanium and near‐ α alloys at cryogenic temperatures remain unclear. This study presents a comparative analysis of the microstructural deformation of a multicomponent near‐ α titanium alloy (Ti‐551) and commercially pure titanium (TA1) subjected to cryogenic rolling at 77 K with a 12% total thickness reduction at ≈6 s −1 . The microstructural evolution was investigated using electron backscatter diffraction and quantitative geometrically necessary dislocation (GND) analysis based on the Nye tensor. Results demonstrate distinct cryogenic deformation modes. TA1 reveals a twinning‐dominated deformation phenomenon, governed by the nucleation and growth of abundant {11–22} compression twins to accommodate local stress concentrations. In contrast, Ti‐551 exhibits a slip‐dominated mode characterized by strongly suppressed twinning; notably, the fraction of {11–22} twins accommodating c‐axis strain decreased to merely 0.35%. Furthermore, in the absence of twinning‐mediated stress relief, Ti‐551 accommodates plastic strain gradients through the accumulation of high‐density GNDs, together with the compensatory activation of basal and high‐energy pyramidal ⟨c + a⟩ slip. These findings provide a mechanistic theoretical basis for optimizing cryogenic processing and tailoring alloy compositions to develop high‐performance titanium alloys.