Design and characterization of new Cu alloys to substitute Cu–25%Ni for coinage applications

As the material and manufacturing cost of coins approached or even exceeded the face value of coins over the last 10 years, the needs to develop less-expensive alloys to replace the current coinage materials increased. The objective of this study is to develop new cost-effective alloys with the same vending machine acceptability and similar color tone as Cu–25%Ni coins. Cu–Zn–Ni–Fe and Cu–Zn–Ni–Fe–Cr alloys developed in this study were found to have the electrical conductivity close to and color similar to that of Cu–25Ni. The strengths of the annealed Cu–25.5%Zn–12%Ni–1.5%Fe and Cu–25.5%Zn–12%Ni–1.5%Fe–0.28%Cr alloys were observed to be 451 MPa and 512 MPa, respectively, with excellent ductility, suggesting that these alloys could be substitutive to Cu–25%Ni alloy for other general structural applications as well as coinage application. Both alloys exhibited the typical ductile fracture surfaces. Cu–Zn–Ni–Fe alloy was found to be a better candidate for coins because of the better formability and machinability associated with its moderate strength and excellent ductility.