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

Nanocrystalline Ti and Ti-TiO2 nanocomposites were produced by high pressur e torsion (HPT) of precompacts of Ti powder (21 mu m) and its mixture with TiO2 powder (36 nm). Effects of processing temperature and pressure on mate rial density and microhardness were systematically studied. The HPT process simultaneously consolidated the TI and Ti-TiO2 powders and refined the gra ins to nanometer size. The microstructure of as-processed samples contained high dislocation density, high internal stress, high angle, non-equilibriu m grain boundaries, and texture. Mechanical properties such as microhardnes s increased with increasing density. Tensile testing showed that the as-pro cessed materials were very brittle. High pressure torsion was found to be a promising technique for producing nanocrystalline materials from micromete r-sized metallic powders. (C) 2000 Elsevier Science S.A. All rights reserve d.