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Abstract

Ni is a base component in high-temperature superalloys and Re is one of the key ingredients to improve mechanical properties in Nibased alloys, in particular creep resistance. It is, however, not fully understood how Re affects creep in Ni-based superalloys. Previous studies showed that in the dilute limit there is almost no effect of Re on the diffusivity of the atoms or the mobility of the vacancies. In this study, we extend our investigation to the non-dilute limit of Re by including Re-Re interactions. This enables us to investigate atomic mobilities and segregation behaviour over the entire composition range. We use a kinetic Monte Carlo (KMC) approach to simulate diffusion in Ni-Re alloys. The key parameter in the KMC model are the diffusion barriers, which are strongly dependent of the local atomic configuration. To obtain an accurate and fast evaluation of the configurationdependent diffusion barriers, we combine the KMC model with a cluster expansion (CE) approach. The CE is parametrised using energies from density-functional theory (DFT) calculations for a large number of possible Ni-Re configurations. From the KMC simulations, we then extract diffusion coefficients, evaluate the vacancy mobility as a function of Re concentration.