Grain boundaries amplify local chemical ordering in complex concentrated alloys

TL;DR

This study demonstrates that grain boundaries in complex concentrated alloys act as sites that amplify local chemical order, leading to nanoscale compositional patterns driven by boundary orientation and material-specific tendencies.

Contribution

It reveals how grain boundaries serve as microstructural anchors that enhance chemical ordering and nanopattern formation in complex alloys, supported by atomistic simulations.

Findings

Grain boundaries amplify chemical order and create compositional nanopatterns.

Composition waves develop with vectors normal to the boundary, extending into the grain.

Boundary orientation and alloy type influence the extent of chemical order amplification.

Abstract

Local chemical ordering strongly influences the behavior of complex concentrated alloys, yet its characterization remains challenging due to the nanoscale dimensions and scattered spatial distribution of the ordered domains. Here, we study chemical ordering near grain boundaries, demonstrating they can act as microstructural anchor points that amplify chemical order and drive the formation of compositional nanopatterns. Atomistic simulations reveal the development of composition waves with ordering vectors normal to the boundary plane in two distinct material systems, CrCoNi and NbMoTaW. These waves manifest as periodic enrichment-depletion patterns that reflect the underlying chemical ordering tendencies of each system, but with amplified contrast that extends several nanometers into the grain interior before gradually decaying. By examining multiple grain boundary orientations and alloys, we show that both the interfacial segregation profile and the crystallographic terminating plane govern the extent and character of this amplification. This interplay between boundary-dictated directional ordering and the diffuse, untemplated chemical domain evolution within the grain advances our understanding of interface-mediated ordering phenomena and suggests new opportunities for experimentally detecting local chemical order in complex concentrated alloys.