Effect of composition on the stacking fault energy of copper-nickel alloys using molecular dynamics simulations

Cu-Ni alloys, popularly known as Cupronickel, have gained a variety of interesting applications owing to their excellent corrosion resistance, excellent ductility when annealed and good tensile strength. The Cu-Ni system is a binary isomorphous system, a solid solution of FCC crystal structure exists at all compositions below the solidus. In FCC alloys, the type and amount of alloying has a profound effect on the stacking fault energy (SFE). In the present work, a molecular dynamics simulation technique has been used for creation of stacking fault and determination of SFE. A stacking fault is created in the simulation by the displacement of one atomic plane relative to the rest of the crystal, and the SFE is subsequently computed by the measuring the difference in energy of the system before and after the creation of the fault. The simulation is locally alloyed in the vicinity of the stacking fault and the SFE is plotted as a function of the Ni content. The stacking fault energy was found to increase with an increase the Ni content, conforming to experimental results, from 40 mJ/m2 for pure copper to 70 mJ/m2 for a Cu-Ni alloy with 40 atomic percent Ni.