Shear-strain induced α (hcp) phase to β (bcc) plus ω (simple hexagonal, space group P6/mmm) phase transformation in pure titanium (Ti) occurs during high pressure torsion (HPT) deformation at the pressure of 5 GPa and rotation speed of 0.2 rpm at room temperature. Notably, the β phase remains metastable at ambient temperature and pressure after the HPT load is released. In contrast, prior studies report that the β phase in pure Ti typically forms only at temperatures exceeding 1155 K under ambient pressure or under pressures potentially surpassing 52 GPa at ambient temperature. The present findings provide further insights into shear-strain induced allotropic transformations in pure Ti, providing the basis for understanding the formation and stabilization of high temperature phase or high pressure phase under ambient conditions.
He et al. (Mon,) studied this question.