Effect of severe plastic deformation on the conductivity and strength of copper-clad aluminium conductors

Aluminium rods with different copper sheath thicknesses were processed by severe plastic deformation at room temperature and then annealed, to join the constituent metals and produce a nanocrystalline microstructure. A study of the effects of the deformation parameters, copper cladding thickness and annealing temperature on the electrical conductivity and hardness of the conductors is reported. It is shown that an interface forms between constituents because of intermixing in the course of severe shear deformation under high hydrostatic pressure and diffusion during the subsequent annealing. The effective conductivity of the aluminium copper-clad conductor dropped after deformation, but was recovered during annealing, especially during short annealing at 200 °C, to a level exceeding the theoretically predicted one. In addition, the annealing resulted in increased hardness at the interface and copper sheath.