On the [formula omitted] twin-accommodated mechanisms in equiaxed near β-Ti alloys operating by unidirectional and cross rolling

Abstract

Cross rolling (CR) process was successfully applied to solve the grain refinement of the equiaxed microstructure. In this work, microstructural evolution, textural discrepancy, mechanical properties and twin-accommodated mechanisms were studied in the equiaxed near β titanium alloy for different modes of rolling i.e. unidirectional rolling (UR) and cross rolling (CR). The results showed that CR can effectively promote the grain refinement of both the α and β phases as compared to UR, which leads to weaker texture intensities of the CR sample, and results in an elevated ductility. The {101‾1} twinning is the major twin-accommodated mechanisms observed in near β-Ti alloys. The {101‾1} twinning accommodated the rotation of subgrains and tailored subgrains orientation during the UR process. In comparison, during the CR process, accumulated stress increases the volune fraction of residual activated twins. Furthermore, with the increasing deformation, the α phase was progressively fragmented into fine grains by the thickening and extension of {101‾1} twins. The results in the present study can be applided to optimize deformation processes to achieve ultra-fine grained microstructures, and to figure out the refinement of massive-grained microstructures.