On nanostructured molybdenum-copper composites produced by high pressure torsion

Nano-structured molybdenum-copper composites have been produced through severe plastic deformation of liquid-metal infiltrated Cu30Mo70 and Cu50Mo50 (wt.%) starting materials. Processing was carried out using high pressure torsion at room temperature with no subsequent sintering treatment, producing a porosity-free, ultrafine grained composite. Extensive deformation of the Cu50Mo50 composite via two-step high-pressure torsion produced equiaxed nanoscale grains of Mo and Cu with a grain size of 10-15 nm. Identical treatment of Cu30Mo70 produced a ultrafine, lamellar structure, comprised of Cu and Mo layers with thicknesses of ~5 nm and ~10-20 nm, respectively and an interlamellar spacing of 9 nm. This microstructure differs substantially from that of HPT-deformed Cu-Cr and Cu-W composites, in which the lamellar microstructure breaks down at high strains. The ultrafine-grained structure and absence of porosity resulted in composites with Vickers hardness values of 600 for Cu30Mo70 and 475 for Cu50Mo50. The ability to produce Cu30Mo70 nanocomposites with a combination of high strength, and a fine, oriented microstructure should be of interest for thermoelectric applications.