Microstructure and properties of high strength and high conductivity Cu-0.48Cr-0.20Nb-0.27Zn alloy treated by a new combined thermo-mechanical treatment

Abstract

A Cu-0.48Cr-0.20Nb-0.27Zn (wt.%) alloy with excellent comprehensive performance is designed and prepared by adding Zn element and combining it with a novel combined thermo-mechanical treatment. A high-temperature short-time treatment is introduced to the traditional thermo-mechanical treatment. Results show that the hardness, tensile strength, yield strength, elongation, and electrical conductivity of Cu-Cr-Nb-Zn alloy reach 180HV, 580 MPa, 535 MPa, 7.6%, and 80.2%IACS, respectively. Compared with conventional thermo-mechanical treatment, the alloy after the new process has increased by 15HV, 35 MPa, 40 MPa, 1.3%, and 2.0%IACS, respectively. Submicron grains and nanoscale twins emerge following high-temperature short-time treatment (850 °C/5min), and the grains undergo substantial refinement. Besides, this process promotes the precipitation of solid solution Cr atoms, thereby significantly improving the electrical conductivity of the alloy. Two distinct crystal structures (C14 and C15) of Cr2Nb with diameters ranging from 80 to 200 nm are observed. The alloy's strength is greatly increased in the following aging process, which precipitates a significant quantity of nanoscale Cr phase. All of the above results have certain reference significance for the optimization design of Cu-Cr-Nb alloy composition as well as performance improvement.