Processing nanocrystalline Ti and its nanocomposites from micrometer-sized Ti powder using high pressure torsion

Nanocrystalline Ti and Ti–TiO2 nanocomposites were produced by high pressure torsion (HPT) of precompacts of Ti powder (21 μm) and its mixture with TiO2 powder (36 nm). Effects of processing temperature and pressure on material density and microhardness were systematically studied. The HPT process simultaneously consolidated the Ti and Ti–TiO2 powders and refined the grains to nanometer size. The microstructure of as-processed samples contained high dislocation density, high internal stress, high angle, non-equilibrium grain boundaries, and texture. Mechanical properties such as microhardness increased with increasing density. Tensile testing showed that the as-processed materials were very brittle. High pressure torsion was found to be a promising technique for producing nanocrystalline materials from micrometer-sized metallic powders.