Influence of plastic deformation on evolution of defect structures, microhardness and electrical conductivity of copper

Abstract

Samples of pure Cu cylinder were plastically deformed by the combination of cold forging (CF) and cold drawing (CD) at liquid nitrogen temperature. X-ray diffraction measurements indicate that an increase in deformation strain leads to a decrease in crystallite size and an increase in twin densities for the CF and CD processed ultrafine grained samples. Dynamic recovery is suggested to start during the deformation process and leads to a decrease in dislocation density at large deformation strains. The increase in twin density could compensate the loss of microhardness because of the decrease in dislocation density. The electrical conductivities of CF+CD samples were tested through standard four-probe method, all of which are higher than 92% the International Annealed Copper Standard. The results suggest that the strength of pure Cu could be improved and still keep its relatively high electrical conductivity by introducing deformation twins into its microstructure.