Short-Range Order Effects in High-Entropy Alloys

High-entropy alloys (HEAs) are multicomponent metallic systems whose near-equiatomic compositions give rise to exceptionally high configurational entropy. Contrary to the idealised random solid-solution paradigm, atomic interactions promote local chemical correlations known as short-range order (SRO), typically spanning only a few atomic distances. SRO manifests as preferential pairing or clustering of certain elements that alter the local energy landscape, thereby influencing fundamental processes such as dislocation motion, phase transformations and fault energies. These local architectures can form during thermal treatments, mechanical loading or a combination of both, and they play a pivotal role in tailoring strength, ductility and fatigue resistance. Recent advances have revealed the existence of medium-range order linking incipient SRO domains, and the emergence of pseudo-composite microstructures when clusters of differing lattice symmetries coexist within a single phase. Understanding and manipulating SRO in HEAs opens a route to design alloys that achieve an optimal balance of mechanical performance, corrosion resistance and thermal stability, with implications for energy, aerospace and transport applications.

Research from Nature Portfolio

Advanced electron-diffraction data-mining combined with neutron scattering and atom probe tomography has uncovered two distinct modes of SRO in a CrCoNi alloy. Homogenised samples exhibit alternating close-packed planes minimising Cr–Cr pairs, whereas heat treatment promotes L12-type clusters, each variant profoundly affecting dislocation slip and strength. Mechanical loading at cryogenic temperature in a multi-principal-element FeMnCrCo alloy induces deformation-driven SRO. Transmission electron microscopy and simulation studies reveal that this mechanically derived ordering can be tuned via strain rates, with limited impact on yield strength but noticeable effects on twinning and strain-induced transformations. In a CoCuFeNiPd HEA, Monte Carlo and density-functional calculations predict an energetically favourable SRO that self-organises into a pseudo-composite microstructure. Distinct clusters act respectively as hard and soft fillers within a continuous matrix, delivering simultaneous enhancements in ultimate strength and ductility.

Short-Range Order Effects in High-Entropy Alloys publication trend

The graph below shows the total number of articles in short-range order effects in high-entropy alloys across all publications each year (not limited to Nature Index journals).

Technical terms

Short-range order (SRO): Localised, non-random arrangement of atoms over a few nearest-neighbour distances that departs from an ideal random solid solution.

Chemical medium-range order (CMRO): Correlation of atomic occupancies extending beyond nearest neighbours yet lacking long-range periodicity.

Atom probe tomography (APT): High-resolution microscopy technique generating three-dimensional maps of elemental composition at near-atomic scale.

Pseudo-composite microstructure: Morphology in a single-phase alloy where clusters with contrasting lattice preferences function as reinforcement and ductile regions.

References

1. Machine Learning‐Enabled Tomographic Imaging of Chemical Short‐Range Atomic Ordering. Advanced Materials (2024).
2. Data-driven electron-diffraction approach reveals local short-range ordering in CrCoNi with ordering effects. Nature Communications (2022).
3. Mechanically derived short-range order and its impact on the multi-principal-element alloys. Nature Communications (2022).
4. Simultaneously enhancing the ultimate strength and ductility of high-entropy alloys via short-range ordering. Nature Communications (2021).
5. Chemical domain structure and its formation kinetics in CrCoNi medium-entropy alloy. Acta Materialia (2022).