Enhancing strength and electrical conductivity of Cu–Cr composite wire by two-stage rotary swaging and aging treatments

The wide application of Cu–Cr composites is greatly limited by their trade-off of tensile strength and electrical conductivity. In this work, we employed an industrial method of rotary swaging (RS) and subsequent aging to improve the combination of strength and electrical conductivity of Cu-3.11Cr composite wire and reveal the microstructural evolutions during the processes. It is found that the matrix grains of Cu-3.11Cr have been significantly refined and elongated during the deformation and a fibrous structure has been formed. The average diameter of the grains has been reduced to about 3.9 μm after RS processing for an equivalent strain ∼3.5. Moreover, most of the initial micron sized Cr particles are elongated severely along axial direction which plays a role of fiber composite strengthening and reduces the scattering effect of electrons. Besides, lots of nano sized Cr particles re-precipitated in the matrix during the subsequent aging process. After the two-stage swaging and aging, the Cu-3.11Cr composite wire obtained a good comprehensive property with an ultimate tensile strength of 580 MPa and the electrical conductivity of 81.1% IACS (international annealed copper standard). We rationalized the high strength is attributed to dislocation, grain refinement, dispersion and precipitation as well as fiber-composite strengthening. The precipitation of Cr atoms from the Cu matrix during the aging treatment is vital for the enhancement of the electrical conductivity without loss of strength. These findings can provide some new insights in the mass production of the high performance Cu–Cr composites.