effect of thermomechanical treatment on structural phenomena and ELECTROCONDUCTIVITY in copper conductors

Abstract

Despite its relatively high cost, copper is still the most popular electroconductive material. Its electroconductivity can be affected via structure modifications introduced by shear mixing, i.e. deformation processing, and/or thermomechanical treatment. Being an industrially applicable method of intensive plastic deformation, advantageously used to impart shear mixing, rotary swaging is favourable for production of long electroconductive wires. This study is focused on assessment of the effects of thermomechanical treatment on structural phenomena within copper conductors; the treatment consisted of room temperature rotary swaging and subsequent annealing. The results showed that the deformation ratio introduced via swaging was sufficient to impart homogenization of structure as the differences between the grain sizes and texture orientations within the peripheral and axial regions of the conductor were minimal. On the other hand, the swaged and annealed conductor featured slight inhomogeneity between the peripheral and axial regions, especially as regards structure regeneration and the occurrence of twinning, which was more pronounced in the axial region of the thermomechanically processed conductor (the volume fraction of <111> 60° twin boundaries was 60 % within this sample region). Interestingly, the electroconductivity was higher than 100 % IACS (International Annealed Copper Standard) for the swaged conductor, and even increased up to 104.4 % IACS for the annealed conductor due to the structure modifications imparted by the applied heat treatment.