Fabrication of high strength Cu–NbC composite conductor by high pressure torsion

A high strength Cu–NbC composite conductor for electrical applications was fabricated from Cu, Nb and C elemental powders using high pressure torsion (HPT). After HPT, samples showed close to full density (>99%). SEM observations revealed that atomic scale mixing occurred in the following order: deformation of Cu particles, the formation of Cu/Nb lamellar structure, fracturing of Nb lamella into sub-micron particles and the formation of uniform structure with fine distribution of Nb particles. The in situ formation of NbC in the copper matrix during HPT was detected. Annealing at 600 and 700 °C resulted in substantial increases in microhardness and tensile strength and a slight decrease in electrical conductivity with increasing NbC volume fraction. The best combination of electrical conductivity (54% IACS) and tensile strength (810 MPa) ever reported for such a composite was obtained in the Cu–2 vol% NbC composite after annealing at 700 °C.