Microstructure evolution of commercial-purity titanium during cryorolling

Abstract

Electron backscatter diffraction and transmission electron microscopy have been used to analyze the microstructural evolution of titanium during rolling at a cryogenic temperature (T = −196°C). It has been found that intensive twinning at the cryogenic deformation temperature accelerates the kinetics of microstructure refinement. The quantitative analysis of microstructure evolution in titanium upon cryorolling has shown that structure evolution is mainly related to mechanical twinning in the initial stages. A substructure is developed and deformation-induced high-angle boundaries are formed in the range of mean and high degrees of deformation. It was established that rolling to the total degree of deformation ɛ = 93 % (e = 2.6) at T = −196°C leads to the formation of a titanium microstructure with a grain/subgrains size of approximately 80 nm. The contribution of mechanical twinning and dislocation gliding in structural transformations in titanium with increasing degree of deformation during cryorolling is discussed.