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

Abstract

Nanocrystalline Ti and Ti–TiO 2 nanocomposites were produced by high pressure torsion (HPT) of precompacts of Ti powder (21 μm) and its mixture with TiO 2 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–TiO 2 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.