A modified Hall-Petch relationship in ultrafine-grained titanium recycled from chips by equal channel angular pressing

Equal channel angular pressing was used to consolidate commercially pure titanium chips into fully dense bulk material with high strength (up to 650 MPa), due to an ultrafine grain size as low as 0.8 μm, and good ductility (∼16%). Electron backscattered diffraction was employed to reveal low-angle grain boundaries (LAGBs), enabling a modified Hall–Petch relationship to be analyzed in consideration of strengthening contributions from LAGBs in particular, but also interstitial solutes, high-angle grain boundaries and potential oxide dispersion.