Mechanical properties of Cu–Cr system alloys with and without Zr and Ag

The effects of addition of Zr and Ag on the mechanical properties of a Cu–0.5 wt%Cr alloy have been investigated. The addition of 0.15 wt%Zr enhances the strength and resistance to stress relaxation of the Cu–Cr alloy. The increase in strength is caused by both the decrease in inter-precipitate spacing of Cr precipitates and the precipitation of Cu5Zr phase. The stress relaxation resistance is improved by the preferentially forming Cu5Zr precipitates on dislocations, in addition to Cr precipitates on dislocations. The addition of 0.1 wt%Ag to the Cu–Cr and Cu–Cr–Zr alloys improves the strength, stress relaxation resistance and bend formability of these alloys. The increase in strength and stress relaxation resistance is ascribed to the decrease in inter-precipitate spacing of Cr precipitates and the suppression of recovery during aging, and to the Ag-atom-drag effect on dislocation motion. The better bend formability of the Ag-added alloys is explained in terms of the larger post-uniform elongation of the alloys.