Short-range order in face-centered cubic multi-principal element alloys: identification, structure–property relationships, and superfunctional implications

Abstract

Multi-principal element alloys have emerged as an important class of structural materials owing to their exceptional combinations of strength, ductility, and microstructural stability. Increasing evidence suggests that chemical short-range ordering plays a critical role in governing these properties by modifying local bonding, defect energetics, and deformation pathways. Yet, a coherent understanding of short-range order in face-centered cubic multi-principal element alloys remains elusive, not only because its formation and manifestation are highly sensitive to alloy chemistry and thermal history, but also because fundamental questions remain unresolved regarding how short-range order should be defined, measured, and interpreted in chemically complex solid solutions. In particular, the rigorous distinction of short-range ordering from clustering, deformation-induced local ordering, long-range ordered precipitates, and diffraction-related artifacts remains a central challenge in the field. In this review, we critically examine the current understanding of short-range order in face-centered cubic multi-principal element alloys, with emphasis on its thermodynamic origin, thermal evolution, quantitative descriptors, and multiscale characterization. A distinctive contribution of this review is the proposal of a practical correlative protocol for identifying “true short-range order”, with emphasis on the minimum evidence required to distinguish genuine short-range order from clustering, long-range ordered precipitates, and measurement-related artifacts. Particular attention is devoted to recent advances in atomistic modeling, atom probe tomography, and transmission electron microscopy-based approaches, which have expanded access to local chemical ordering while also exposing important methodological limitations. We further assess how short-range order perturbs defect energetics, dislocation behavior, stacking-fault-mediated deformation, strengthening, and other kinetic processes across multiple length scales. By integrating recent advances with current controversies, this review seeks to clarify the conditions under which short-range ordering can be identified rigorously, linked defensibly to measurable properties, and ultimately used as a tunable microstructural design parameter in high-performance and superfunctional high-entropy materials.