Microstructure and properties of a Cu–Ni–Si–Co–Cr alloy with high strength and high conductivity

A novel Cu-1.01%Ni-0.28%Si-0.14%Co-0.45%Cr (mass percent) alloy with high strength and high conductivity was fabricated. Microstructure, mechanical and electrical properties of the alloy after multi-stage thermo-mechanical treatment were investigated in detail. The alloy has excellent comprehensive properties, with a tensile strength of 810 MPa, yield strength of 777 MPa, elongation of 3.4%, and electrical conductivity of 57.5%IACS (International Annealing Copper Standard). Three kinds of precipitates, (Cr,Co)2Si, (Ni,Co)2Si and Cr, form during aging treatment. Addition of Co element promotes the precipitation of Cr, Ni and Si solute elements from the matrix, while inhibits the growth of the (Cr,Co)2Si. The high strength of the alloy treated by multi-stage thermo-mechanical process is attributed to the dispersion strengthening, sub-structure strengthening, and work-hardening. The multi-aging process and addition of Co effectively improve the electrical conductivity of the studied alloy. The high strength and high conductivity of studied alloy make it as a potential candidate for lead frame materials in electrical and electronics industry.