Microstructure and mechanical properties of high purity nanostructured titanium processed by high pressure torsion at temperatures 300 and 77 K

Several structural states of nanostructured high purity Ti with average grain size down to 100 nm were achieved by high pressure torsion (HPT) at temperatures 300 and 77 K. As a result of HPT processing, changes of crystallographic texture, of grain and crystallite size, and of the dislocation density have been measured and analyzed. Mechanical properties of the nanostructured Ti were studied by uniaxial compression at temperatures 300, 77, and 4.2 K. The texture components indicate simple shear deformation arising from HPT. With subsequent compression, the yield strength appears to be governed by the grain size rather than by crystallite size, dislocation density, and/or impurity content. Considerable changes of texture were observed after low temperature compressive deformation indicating that twinning markedly contributes to plasticity.