Microstructure and properties of nanocrystalline copper-niobium alloy with high strength and high conductivity

A nanocrystalline Cu-10 wt%Nb alloy, with high strength and high conductivity, was prepared by mechanical alloying and subsequent hot pressing. The microstructure and properties of the alloys after consolidation at different temperatures were investigated. The alloy, subjected to hydrogen-annealing of milled powders at 560 °C for 1 h and then vacuum hot-pressing sintering under 30 MPa pressure and 900 °C for 2 h, has a microhardness of 334 HV, a tensile strength of 1102 MPa, a yield strength of 1043 MPa, and an electrical conductivity of 57% IACS (International Annealing Copper Standard). The as processed alloy is characterised by Nb nanoparticles dispersed in the nanocrystalline Cu matrix. The high strength of Cu-Nb alloy is related with the microstructure, i.e. the nanocrystalline grains produce the grain boundary strengthening, while the Nb nanoparticles produce the precipitation strengthening. The grain boundaries and the nanoparticles are also found to influence the electrical conductivity of the alloy considerably.