Equal-channel angular pressing and high-pressure torsion of pure copper: Evolution of electrical conductivity and hardness with strain

Pure Cu (99.99%) is processed by equal-channel angular pressing (ECAP) and by high-pressure torsion (HPT). The electrical resistivity as well as the microhardness increases with an increase in the equivalent strain at an early stage of straining, but saturates to a steady state at the equivalent strains more than ̃20. At the steady state, the samples processed by ECAP and HPT show a significant increase in the hardness (̃270%) but little decrease in the electrical conductivity (̃12%) when compared to the annealed state. Transmission electron microscopy confirms that the microstructure does not change at the saturated level with further straining. Evolutions of hardness, electrical conductivity and microstructures are also investigated after post-HPT annealing.