Evolution of misorientation distribution during warm ‘abc’ forging of commercial-purity titanium

The evolution of the Misorientation Distribution Function (MDF) during severe plastic deformation (SPD) of titanium at 400 °C was determined. Deformation was carried out by the successive compression of prismatic samples along three orthogonal directions. In all cases, the strain increment was 40%; total deformation comprised up to 12 such increments. For small total strains, low-angle boundaries (LABs) were predominant in the MDF, and the distribution of high-angle boundaries (HABs) depended strongly on the development of {1 0 1¯ 1} twins. The misorientation axes of the LABs were aligned with the 〈0 0 0 1〉〈0 0 0 1〉 direction. The fraction of HABs increased steadily during repeated straining, and their final distribution was close to random. Twins were observed after every straining step. HABs were unstable with respect to strain; their misorientations changed significantly during plastic flow. It was established that the change of the strain path associated with ‘abc’ forging retards the kinetics of the evolution of the MDF.