Place: DPG Spring Meeting 2015, Berlin
High-temperature properties of Ni-base superalloys are known to be highly dependent on the alloying additives, in particular on the presence of Re. Current knowledge of the mechanisms behind this effect is mostly phenomenological in nature and the details of solute diffusion, interaction with various defects (e.g. interfaces, vacancies, and dislocations) as well as the interplay between composition and microstructure are not well understood.
We have analyzed concentration/temperature-dependent diffusion behavior of selected alloying elements in the dilute limit using a combination of density-functional theory calculations and kinetic Monte Carlo simulations . We found that the diffusion of vacancies, which was speculated to be at the core of the Re effect in literature, is only weakly influenced by the presence of the solute elements at concentrations below 3wt%.
At higher solute concentrations solute-solute interactions need to be taken into account. Here we present developments on a cluster expansion approach for non-dilute systems which allows an ab-initio treatment of diffusion in presence of configurational disorder. We further discuss avenues for the treatment of multicomponent systems.  S. Schuwalow, J. Rogal, R. Drautz, J. Phys.: Condens. Matter 26 (2014) 485014.