Precipitation strengthening in Cu-Ni-Si alloys modeled with ab initio based interatomic potentials.

Effective interaction potentials suitable for Cu/δ-Ni ₂ Si and Cu/β-Ni ₃ Si are developed. We optimise the potential parameters of an embedded atom method potential to reproduce forces, energies, and stresses obtained from ab initio calculations. Details of the potential generation are given, and its validation is demonstrated. The potentials are used in molecular dynamics simulations of shear tests to study the interactions of edge dislocations with coherent δ-Ni ₂ Si and β-Ni ₃ Si precipitates embedded in a copper matrix. In spite of significantly different crystallographic structures of copper and δ-Ni ₂ Si which usually result in circumvention of dislocations, we also observed cutting processes in our simulations. Dislocations cut for a specific orientation of the δ-Ni ₂ Si precipitate and in some cases where dislocation loops originating from previous circumvention processes are present in the glide plane. It is found that β-Ni ₃ Si precipitates have a similar effect on precipitation strengthening as δ-Ni ₂ Si. Dislocations usually cut β-Ni ₃ Si but increased coherency strain can lead to circumvention processes.