Chemical order transitions within extended interfacial segregation zones in NbMoTaW

TL;DR

This study uses atomistic modeling to explore extended segregation zones and structural transitions at grain boundaries in NbMoTaW alloys, revealing complex chemical patterning and size-temperature effects on segregation.

Contribution

It provides new insights into the size, structure, and chemical ordering within extended segregation zones in complex concentrated alloys, highlighting phenomena not seen in simpler systems.

Findings

Extended segregation zones are larger than traditional regions.

Structural A2-to-B2 transitions occur within these zones.

Grain size and temperature significantly influence zone widths.

Abstract

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.