Severe plastic deformation (SPD) of titanium at near-ambient temperature

Abstract: Severe plastic deformation of titanium at near-ambient temperature has been realized using large-strain machining. The material that received the highest levels of strain, the chip, is found to have a nanocrystalline structure with ∼100nm sized grains. This microstructure is finer than that observed in titanium following equal channel angular pressing at elevated temperatures. The machined surface of the workpiece is found to have a graded microstructure composed of ultrafine grains at and near the surface and a preponderance of twins further into the subsurface. The parameters of the large-strain deformation field, namely strain rate and strain, are obtained using an adaptation of a particle image velocimetry technique. The microstructure characteristics are shown to be a consequence of the deformation field parameters, which activate both twinning and dislocation-mediated mechanisms of plastic flow. [Copyright &y& Elsevier]