The dynamic responses of lamellar and equiaxed near β-Ti alloys subjected to multi-pass cross rolling

This work gives a comparison on the microstructural characteristics, textural discrepancies, and twinning behaviors of lamellar and equiaxed near β-Ti alloys during multi-pass cross rolling with a rolling reduction of 20 %, 50 % and 80 %. The results showed that the restoration mechanism of the alloy in β phase is strongly dependent on the α morphologies, and in comparison, strain path has weaker influences on the grain refinement of the β matrix. Therefore, the texture intensities of both α and β phases were weakened owing to the dynamic recrystallization (DRX) of the two phases in the equiaxed microstructure. While, with regard to the lamellar microstructure, dynamic recovery (DRV) of the β phase predominated, forming elongated β subgrains. Besides, the α and β matrix in lamellar microstructures obeyed the Burgers orientation relationship, which was gradually broken down until the final reduction. Lastly, the 11¯01 twinning exhibits a strong size effect. With the continuous DRX of α phases, the α-twinning is suppressed owing to progressive grain refinement. The activation of β-twinning, namely 332〈113〉 and 112〈111〉, in near β-Ti alloys is heavily dependent on the deficient β-stabilizing elements and the local stress concentration. These findings provide an effective way to obtain ultra-fine grain microstructures of this alloy.