The effect of iron on the microstructure and mechanical properties of a cast Cu–12Sn-1.5Ni (wt. %) alloy

Abstract Effect of Fe content on microstructure and mechanical properties in a gravity-cast Cu–12Sn-1.5Ni (wt. %) alloy has been investigated. Addition of 0.053, 0.63 and 1.44 wt % Fe caused grain refinement, vanishment of continuous interdendritic δ phase, and formation of nano-sized iron precipitates within the dendritic matrix. There was a simultaneous increase in the yield and tensile strength, uniform and total elongation and hardness of Cu–12Sn-1.5Ni-(0.05–1.5)Fe alloys relative to their Fe-free counterpart. Fracture surface analysis revealed an intergranular fracture along the interdendritic δ phase in Cu–12Sn-1.5Ni alloy. But in Cu–12Sn-1.5Ni-(0.05–1.5)Fe alloys, after initiation at interdendritic area, crack propagated into the dendrite matrix in a dimple rupture mode. The evolution mechanism of mechanical properties upon alloying content was discussed in terms of the microstructure characterization, analysis of strain-hardening rate, fractographic examination, as well as the strengthening model. This work sheds light on the alloying effect of minor Fe below 1.0 wt % on the microstructure-mechanical optimization in tin bronze alloys.