Synergistic enhancement of strength and electrical conductivity in Cu–Ni–Si–Co–Ag–Mg alloys via tailored thermo-mechanical processing

Abstract

This study systematically investigated the effects of thermomechanical processing parameters on the precipitation behavior, microstructural evolution, mechanical properties, and electrical conductivity of a Cu-Ni-Si-Co-Ag-Mg alloy. The influence of the number of rolling-aging cycles on the microstructure and properties of the alloy was examined. With increasing cycles, both strength and electrical conductivity increased. After four cycles, the alloy achieved an ultimate tensile strength of 839 MPa, a yield strength of 815 MPa, and an electrical conductivity of 51.8% IACS. Compared to the single-cycle treatment, this represents an increase of 84 MPa in ultimate tensile strength, 76 MPa in yield strength, and a 67.6% improvement in electrical conductivity. Further microstructural analysis revealed that the number of cycles had no significant effect on the grain size of the alloy, while the dislocation density showed a decreasing trend with increasing cycles. Most importantly, as the number of cycles increased, the number of nanoscale precipitates in the alloy increased significantly and their distribution became more uniform. These high-density nanoscale precipitates effectively pinned dislocations and retarded grain recovery, thereby maintaining a relatively high dislocation density to some extent. Precipitation strengthening, work hardening, fine-grain strengthening, and solid-solution strengthening acted together to simultaneously improve strength and electrical conductivity.