Microstructure and properties of Cu-Zn-Cr-Zr alloy treated by multistage thermo-mechanical treatment

A high-strength and high-conductivity Cu-0.4Zn-0.35Cr-0.2Zr alloy was designed and prepared by adding galvanized scrap copper into Cu-Cr-Zr alloy. The effects of multistage thermo-mechanical treatment involving the microstructure and properties of the alloy were investigated by some means, e.g. mechanical property, conductivity testing and transmission electron microscopy observation. After multistage thermo-mechanical treatment, the Cu-Zn-Cr-Zr alloy had tensile strength of 672 MPa, yield strength of 670 MPa, hardness of 201 HV, and electrical conductivity of 72.1 %IACS. Zn was uniformly dissolved in the Cu matrix, and the nano-Cr phase was the main precipitation phase. The strengthening mechanism of the alloy was combination of strain strengthening, fine grain strengthening, precipitation strengthening and solid solution strengthening. Adding an appropriate amount of Zn can improve the strength of the alloy without significantly reducing the electrical conductivity in combination with the appropriate thermo-mechanical treatment. The novel formulation could present an idea for high-quality reuse of waste copper containing Zn to fabricate high-performance copper alloys.