  Interfacial segregation and chemical short-range ordering influence the
behavior of grain boundaries in complex concentrated alloys. In this study, we
use atomistic modeling of a NbMoTaW refractory complex concentrated alloy to
provide insight into the interplay between these two phenomena. Hybrid Monte
Carlo and molecular dynamics simulations are performed on columnar grain models
to identify equilibrium grain boundary structures. Our results reveal extended
near-boundary segregation zones that are much larger than traditional
segregation regions, which also exhibit chemical patterning that bridges the
interfacial and grain interior regions. Furthermore, structural transitions
pertaining to an A2-to-B2 transformation are observed within these extended
segregation zones. Both grain size and temperature are found to significantly
alter the widths of these regions. Analysis of chemical short-range order
indicates that not all pairwise elemental interactions are affected by the
presence of a grain boundary equally, as only a subset of elemental clustering
types are more likely to reside near certain boundaries. The results emphasize
the increased chemical complexity that is associated with near-boundary
segregation zones and demonstrate the unique nature of interfacial segregation
in complex concentrated alloys.
