Improvement in strength and electrical conductivity of Cu–Ni–Si alloys by aging and cold rolling

In order to find the optimum conditions to obtain copper–nickel–silicon (Cu–Ni–Si) alloys with high strength and high electrical conductivity, the aging characteristics of micro-Vickers hardness and electrical resistivity of different Cu–Ni–Si alloys were systematically measured at room temperature. The alloys were isochronally or isothermally aged after solution treatment. The effects of cold rolling after solution treatment as well as the alloy composition on the hardness and resistivity were studied. The results show that there appears to be an optimum composition ratio of nickel to silicon for obtaining high strength and high electrical conductivity, and cold rolling after solution treatment is effective in increasing the strength and electrical conductivity. The addition of a small amount of iron to the copper base alloys appears to improve these above-mentioned properties. A multi-step aging process coupled with cold rolling was proposed for realizing Cu–Ni–Si alloys with high strength and high electrical conductivity. The mechanism of precipitation in cold-rolled alloys was discussed on the basis of the results obtained.