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Abstract

The formation of topologically close-packed (tcp) phases in Ni-based superalloys leads to the degradation of the mechanical properties and is attributed to high local concentrations of refractory elements. It is well known that the structural stability of these phases is driven by the average d-band filling. We demonstrate that this structural trend can be understood with a canonical d-band tight-binding model by comparing to our extensive density-functional theory calculations for tcp phases. In order to understand the precipitation of tcp phases, we investigate the structure and energetics of interfaces between the cubic phases bcc and fcc and the topologically close-packed phases σ and A15. In particular, we employ analytic bond-order potentials (BOPs) that provide an approximation to the tight-binding model and are suitable for large-scale atomistic simulations. We demonstrate the applicability of recently parametrised BOPs for refractory elements to the description of tcp phases at elevated temperatures and report on the first dynamic simulations of interfaces between cubic phases and topologically close-packed phases.