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 beta-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 beta phase is strongly dependent on the alpha morphologies, and in comparison, strain path has weaker influences on the grain refinement of the beta matrix. Therefore, the texture intensities of both alpha and beta 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 beta phase predominated, forming elongated beta subgrains. Besides, the alpha and beta matrix in lamellar microstructures obeyed the Burgers orientation relationship, which was gradually broken down until the final reduction. Lastly, the {1 (1) over bar 01} twinning exhibits a strong size effect. With the continuous DRX of alpha phases, the alpha-twinning is suppressed owing to progressive grain refinement. The activation of beta-twinning, namely {332} (113) and {112} (111), in near beta-Ti alloys is heavily dependent on the deficient beta-stabilizing elements and the local stress concentration. These findings provide an effective way to obtain ultra-fine grain microstructures of this alloy. (C) 2020 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.