Achieving high strength and high electrical conductivity in Cu-Cr-Zr alloy by modifying shear banding during rolling

Abstract

An economical and practical thermomechanical process that is able to achieve a good combination of strength and conductivity is highly desired for the copper alloys. Here, a new multi-stage thermomechanical treatment, characterized by a pre-rolling with small strain followed by a short-time aging before the secondary rolling and aging, is implemented in the Cu-Cr-Zr alloys. Its effect on the mechanical and electrical properties of the alloy is investigated, as well as the mechanism for improving the properties. Strength and ductility are improved at the expense of only a little electrical conductivity compared to those alloys that have undergone conventional single-stage thermomechanical treatment. The pre-rolling and pre-aging result in dense, dispersive and stable shear bands, which contain lots of dislocations and fine grains. Dislocation strengthening is the main reason for the increased yield strength, while heterostructure consisting of microstructures inside and outside the shear bands gives the processed alloys good tensile plasticity. Our studies shed some lights on development of a short and cost saving thermomechanical process for the Cu-Cr-Zr alloys.