Microstructural Evolution and Mechanical Properties of High-Entropy Alloys

High-entropy alloys (HEAs) constitute a distinct class of metallic materials characterised by multiple principal elements in near-equiatomic proportions. The large configurational entropy in these systems stabilises simple solid-solution phases—often face-centred cubic (FCC), body-centred cubic (BCC) or dual-phase structures—suppressing the formation of brittle intermetallics. Microstructural evolution in HEAs is driven by processes such as casting, thermo-mechanical deformation, recrystallisation and ageing. Grain refinement and controlled precipitation (for example B2 secondary phases) arise through careful manipulation of deformation routes and annealing temperatures. Core strengthening mechanisms include solid-solution hardening, Hall–Petch grain-boundary strengthening, precipitation hardening and lattice distortion. The combination of high strength, good ductility and thermal stability underpins the global interest in HEAs for aerospace components, energy systems, cryogenic applications and wear-resistant coatings. Recent advances have emphasised the interplay between sluggish diffusion kinetics, cocktail effects in alloy design and tailored heat-treatment protocols to achieve bespoke performance.

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Microstructural Evolution and Mechanical Properties of High-Entropy Alloys publication trend

The graph below shows the total number of articles in microstructural evolution and mechanical properties of high-entropy alloys across all publications each year (not limited to Nature Index journals).

Technical terms

High-entropy alloy: An alloy system containing five or more principal elements in near-equiatomic proportions, maximising configurational entropy to stabilise simple solid solutions.

Configurational entropy: A thermodynamic measure of disorder due to mixing of multiple elements on crystallographic sites, which can stabilise single-phase structures at elevated temperatures.

Hall–Petch relationship: An empirical relation describing how yield strength increases with decreasing grain size, reflecting the barrier effect of grain boundaries on dislocation motion.

Recrystallisation: A heat-driven process by which new strain-free grains nucleate and grow within a deformed matrix, reducing dislocation density and refining microstructure.

B2 precipitate: An ordered, body-centred cubic secondary phase (often based on NiAl or similar chemistries) that forms within an FCC matrix to strengthen alloys via precipitation hardening.

References

1. High entropy alloys: Key issues under passionate debate. Scripta Materialia (2020).
2. A Study on the Hall–Petch Relationship and Grain Growth Kinetics in FCC-Structured High/Medium Entropy Alloys. Entropy (2019).
3. Microstructural Evolution and Tensile Properties of Al0.3CoCrFeNi High-Entropy Alloy Associated with B2 Precipitates. Materials (2022).
4. Control of the Microstructure in a Al5Co15Cr30Fe25Ni25 High Entropy Alloy through Thermo-Mechanical and Thermal Treatments. Metals (2023).
5. Recrystallization tuning to optimize mechanical properties in heavily rolled CoCrFeNi medium entropy alloy. Journal of Alloys and Compounds (2023).