Consolidation of nanometer sized powders using severe plastic torsional straining

Severe Plastic Deformation (SPD) via torsional straining was used to consolidate nanometer-sized metallic powders and metal-ceramic nanocomposites at room temperature. Materials processed using this technique included copper, Al and nanocomposites based on these metallic nanopowders and SiO2, SiC and Al2O3 nanopowders. The as-processed materials were nearly fully dense. Transmission electron microscopy (TEM) and microhardness measurements were used to characterize the materials. The as-consolidated materials had a grain size smaller than the average particle size of starting powder, indicating grain refinement during severe plastic torsional straining. Due to the oxidation of the initial nanometer sized powders, the as-processed samples were very brittle. Thermal stability was investigated by annealing the as-consolidated samples at various temperatures and then measuring their microhardness. (C) 1998 Acta Metallurgica Inc.