Asymmetric Cryorolling and Subsequent Low-Temperature Annealing to Improve Mechanical Properties of TA2 Ti Sheets

Commercially pure titanium sheets with high strength and elongation were produced via asymmetric cryorolling and subsequent low-temperature short-time annealing. Results show that the yield strength of the asymmetric cryorolled TA2 Ti sheets with an average grain size of 460 nm reached 892 ± 13 MPa, 170 MPa higher than that of the room-temperature rolled specimens, and their elongation to failure was 6.0 ± 0.9%. After vacuum annealing at 573 K for 30 min, the elongation of the TA2 Ti sheets increased to 13.2 ± 2.0%, and their yield strength was 741 ± 7 MPa. Under the action of additional shear stress at cryogenic temperature, the grain refinement and dislocation accumulation were more significant in the samples subjected to asymmetric cryorolling plus annealing process than those subjected to room-temperature rolling and annealing. Besides, uniform distribution of dislocations and texture, finer grain sizes, and a higher proportion of high angle grain boundaries in samples via asymmetric cryorolling plus annealing provide favorable conditions for uniform plastic deformation and delay the stress concentration during tensile testing. Therefore, the elongations to failure of those samples are similar to the samples subjected to room-temperature rolling plus annealing.