Effect of heat treatment on the highly corrosion-resistant Cu70Ni27.7Fe2.3 alloy

Minor Fe additions are widely added to enhance the corrosion resistance of cupronickel alloys. The present paper aims at optimizing the amounts of Fe in Cu70(Ni,Fe)30 (at.%) alloys using a cluster-plus-glue-atom model for stable solid solutions. By this model, it is assumed that one Fe atom and 12 Ni atoms formed a Fe-centered and Ni-surrounded cube-octahedron cluster and the isolated FeNi12 clusters embedded in a Cu matrix. The stable solid solution alloy composition of Fe-modified Cu70Ni30 alloy was described by a cluster formula [Fe1Ni12]Cu30.3 = Cu70Ni27.7Fe2.3 (at.%). The effect of homogenizing annealing treatment on the microstructure and corrosion resistance was also investigated by XRD, TEM and electrochemical corrosion measurements. The corrosion test indicates that the Cu70Ni27.7Fe2.3 alloy annealed at 800 °C for 5 h possesses the best corrosion resistance in 3.5% NaCl solution.