Evolution of grain and subgrain structure during cold rolling of commercial-purity titanium

Research highlights: → EBSD analysis of cold-rolled titanium revealed three stages of structure evolution. → These stages are defined by plots of the boundaries density as a function of strain. → The first stage is associated with twinning. → Dislocation density increases and substructure forms at the second stage. → The third stage is related to the formation of high-angle boundaries. - Abstract: The evolution of microstructure in commercial-purity titanium during cold rolling to a thickness strain of 2.6 was quantified using electron backscatter diffraction. The measurements were analyzed in terms of the mean grain size and the density of boundaries (the ratio of total boundary length to the scanned area). The density of high-angle boundaries as a function of thickness strain had three distinct stages, each of which was associated with a different mechanism of microstructure formation, i.e., (i) twinning, (ii) an increase in dislocation density and the formation of substructure, and (iii) the formation of deformation-induced high-angle boundaries. The influence of twinning on the kinetics of microstructure evolution was also interpreted.