Effect of Heat Treatment on the Microstructure and Properties of Deformation-Processed Cu-7Cr In Situ Composites

The effect of heat treatment on the microstructure, electrical conductivity, and tensile strength of deformation-processed Cu-7Cr in situ composites produced by thermo-mechanical processing was investigated. The Cr fibers in the Cu-7Cr in situ composite underwent coarsening, break-up, and spheroidization after exposure to elevated temperatures. The conductivity and tensile strength of the in situ composite first increased with increasing isochronal heat treatment temperature, reached a peak value, and decreased at higher temperatures. The isothermal heat treatment temperature was determined to be 625 °C. The Z (Z is an optimization parameter to evaluate the service performance of deformation-processed Cu-based in situ composites) value of the deformation-processed Cu-7Cr in situ composite, at η = 7 (η is a cumulative cold deformation strain) after the heat treatment at 625 °C for 1 h, reached the peak value of 3.46 × 10⁷ MPa² % International Annealed Copper Standard (IACS). The isochronal heat treatment time was determined to be 1 h. The following combination of conductivity and tensile strength of the deformation-processed Cu-7Cr in situ composite with a cumulative cold deformation strain of eight after isochronal aging treatments for 1 h could be attained respectively as (i) 76.0% IACS and 889 MPa; (ii) 76.8% IACS and 876 MPa; or (iii) 77.5% IACS and 779 MPa.