**1. Introduction**

Copper-clad aluminium (CCA) wire is a well-known conductor produced by extrusion of an aluminium rod in a copper can. Al-Cu hybrid materials combine the high conductivity of copper with the lightweight of aluminium. These wires, used in high frequency applications, offer the advantages of better conductivity due to the skin effect, and higher strength and corrosion resistance compared to all-aluminium wire, while costing less than all-copper wire [1]. The well-known study of copper-clad wires [2] shows that at very high frequencies, these wires' electrical properties approach those of a solid copper conductor.

Extrusion of aluminium–copper bi-metallic rods is performed in several reduction steps that are combined with annealing to restore the materials' ductility. The annealing; however, leads to enhanced diffusion between constituents and the formation of brittle aluminium–copper intermetallic compounds at the interface [3,4], which affects the composite wire's conductivity [5,6]. The interface formed between aluminium and copper consists of a number of intermetallic compounds (up to 13 stable intermetallic phases according to Murray [7]), the formation of which depends on the annealing temperature and duration. The conductivity of these phases is shown to be many times lower than that of the constituent materials [5,6].

A different approach, considered here, suggests replacing the extrusion process with a severe plastic deformation (SPD) process [8,9]. We have already used a similar method for aluminium–steel conductors in [10]. Since SPD introduces a gigantic shear strain into the processed material, especially in the vicinity of the interface [11,12], it is expected that the bonding between aluminium and copper will appear at low temperatures due to intermixing. During SPD processing, this brittle intermetallic layer will either not form or be destroyed and dissolved, which would improve the strength and conductivity of the resulting wire. Low-temperature annealing was applied to assist the diffusion and strengthening of the bond region.

In this work, aluminium rods with different copper sheath thicknesses were processed using SDP at room temperature and then annealed. A study of the effect of SPD parameters, copper cladding thickness, and annealing temperature on the electrical conductivity and strength of CCA conductors is reported below.
