Driving Innovation: How High Entropy Alloys Could Shape Future Vehicles?

By Mufaddal Shakir

8/23/20256 min read

High-Entropy Alloys (HEAs) have emerged as one of the most exciting classes of materials in recent years, capturing the attention of materials scientists, automotive engineers, and researchers worldwide. Unlike traditional alloys that are based on one or two principal elements, HEAs are composed of five or more elements in near-equal proportions. This unique chemistry results in a high configurational entropy that stabilizes simple solid-solution phases (FCC, BCC, or HCP), unlocking an extraordinary combination of properties.

In this article, we'll explore:

What are HEAs and their significance?
Different properties of HEAs
Manufacturing methods of HEAs
A comparison of properties with other metals
Applications of HEAs
Unique insights and future trends
Latest research on HEAs

1) What are HEAs?

HEAs, sometimes referred to as Multi-Principal Element Alloys (MPEAs) or Compositionally Complex Alloys (CCAs), represent a paradigm shift in alloy design. Instead of a single dominant element (like Fe in steel or Al in aluminuim alloys), HEAs distribute multiple elements equally, creating stable microstructures with remarkable performance. The resulting high configurational entropy can favour single-phase FCC or BCC solid solutions instead of brittle intermetallics, depending on chemistry and processing.

The classic example is the Cantor alloy (CoCrFeMnNi). It is the best-known HEA. It crystallizes into a single FCC phase and exhibits extraordinary ductility and fracture toughness, especially at cryogenic temperatures. Since then, thousands of HEA systems have been investigated, each with unique microstructures and properties. Some other examples include refractory HEAs such as AlMoNbTaTiZr and NbMoTaW.

Classification of HEAs.

2) Properties of HEAs

The combination of multiple principal elements leads to several distinct strengthening and stability mechanisms that set HEAs apart:

a) Mechanical Properties

Strength and ductility synergy: Unlike conventional alloys, HEAs can exhibit both high strength and high ductility due to mechanisms such as TRIP (Transformation-Induced Plasticity) and TWIP (Twinning-Induced Plasticity). This makes them excellent candidates for crash-resistant automotive applications.
Cryogenic performance: Some HEAs, like the Cantor alloy, retain ductility and toughness even at extremely low temperatures, where most metals become brittle.

b) Thermal Properties

High-temperature stability: Refractory HEAs (Nb, Ta, Mo, W, V-based) retain strength and creep resistance above 1100 °C. This makes them potential alternatives to Ni-based superalloys.
Sluggish diffusion effect: The multiple-element environment slows atomic diffusion, contributing to thermal stability and creep resistance.

c) Corrosion and Oxidation Resistance

HEAs often form protective oxide films due to the presence of Cr, Al, or Si, providing excellent corrosion resistance. This is useful in aggressive environments like engine chambers and exhaust systems.

d) Lightweight Potential

By incorporating Al, Mg, Ti, or Li, researchers have designed Lightweight HEAs (LWHEAs) with densities as low as 5–6 g/cm³, bridging the gap between aluminum alloys and steels while offering higher mechanical strength.

e) Resistance to Hydrogen Embrittlement

HEAs with stable FCC phases exhibit lower hydrogen diffusion rates, reducing susceptibility to hydrogen embrittlement compared to steels.

Figure showing a comparison of tensile strength between HEAs and other materials.

3) Manufacturing Techniques

Processing methods for HEAs are critical because microstructure dictates performance. Each technique offers different advantages:

a) Casting and Thermomechanical Processing

Vacuum arc melting or induction melting is typically used to prepare bulk HEAs. However, segregation and dendritic structures often occur, requiring homogenization.
Rolling, forging, and annealing refine grains, tune dislocation density, and adjust metastability for TRIP/TWIP mechanisms.

b) Severe Plastic Deformation (SPD)

Techniques like Equal Channel Angular Pressing (ECAP), High-Pressure Torsion (HPT), and Friction-Stir Processing significantly refine grains.
SPD can activate unique deformation mechanisms in HEAs, producing ultrafine-grained structures with enhanced hardness and yield strength.

c) Powder Metallurgy

Spark Plasma Sintering (SPS) and Hot Isostatic Pressing (HIP) enable near-net-shape HEAs with fine microstructures and minimized segregation.
Powder metallurgy allows easier processing of difficult-to-melt refractory HEAs.

d) Additive Manufacturing (AM)

Methods like Laser Powder Bed Fusion (LPBF) and Directed Energy Deposition (DED) offer precise control of cooling rates and microstructures.
AM enables fabrication of complex geometries, functionally graded HEAs, and repair of worn components.

e) Surface Engineering and Coatings

Laser cladding, thermal spraying, and PVD coatings deposit HEAs on substrates.
HEA coatings combine hardness, toughness, wear, and corrosion resistance, making them highly suitable for piston rings, valves, brake discs, and gears in automobiles.

4) Comparison of HEAs with Conventional Metals and Alloys

a) Strengthening Mechanisms

Steels/Aluminium/Titanium Alloys: These alloys depend primarily on precipitation hardening, grain refinement, and solid solution strengthening (but from fewer alloying elements).
HEAs: Experience severe lattice distortion because of large atomic size mismatch among elements. This distortion acts as a strong barrier to dislocation motion, enhancing yield strength. Combined with solid-solution strengthening, sluggish diffusion, and twinning-induced plasticity (TWIP), HEAs achieve remarkable strength–ductility balance.

b) Phase Stability

Traditional alloys often form intermetallic compounds or precipitates that improve strength but can reduce ductility.
HEAs suppress intermetallics at equilibrium due to entropy stabilization, allowing them to form single-phase solid solutions even with multiple elements. This gives thermal stability at high temperatures compared to, say, aluminium alloys which lose strength rapidly above 300 °C.

c) High-Temperature Properties

Nickel superalloys are benchmarks for high-temperature creep and oxidation resistance, used in turbines.
Refractory HEAs (Nb–Mo–Ta–W–V systems) show better creep strength and oxidation resistance above 1100 °C due to sluggish diffusion and high melting points.
This gives HEAs a potential edge in replacing costly superalloys in aerospace/automotive turbo components.

d) Corrosion and Wear Resistance

Stainless steels rely on Cr for passivation, aluminum alloys on oxide films, and Ti alloys on TiO₂ layers.
HEAs often contain multiple passivating elements (Cr, Al, Ti, Nb), leading to synergistic passive film formation. Studies show CrMnFeCoNi HEAs outperform 316L stainless steel in chloride-rich environments.

e) Density and Lightweighting

Al- and Mg-based alloys remain lighter (<3 g/cm³) compared to many HEAs (>7 g/cm³).
However, recent lightweight HEAs (Al–Li–Mg–Ti systems) show promise, achieving densities as low as 4–5 g/cm³ with steel-like strength.

f) Economic and Processing Considerations

Traditional alloys are cheaper and benefit from mature, large-scale industrial infrastructure.
HEAs often use expensive refractory or rare metals, and their large-scale processing (casting, AM, coatings) is still developing. Thus, while HEAs provide unmatched property tunability, their economic competitiveness is not yet established for mass-market automotive use.

A comparison of mechanical properties between HEAs and other materials

5) Applications of HEAs in the Automotive Sector

Near-Term Applications

Engine components: HEA coatings on piston rings, valves, and cylinder liners reduce wear and friction.
Brake rotors: HEA-based surface coatings can reduce particulate emissions, aiding compliance with stricter Euro 7 standards.

Mid-Term Applications

Lightweight structural components: LWHEAs offer a balance between weight savings and mechanical robustness for brackets and crash structures.
Additive manufactured HEA parts: Complex components like housings and lattice structures can be fabricated with enhanced properties.

Long-Term Applications

High-temperature components: Refractory HEAs may replace Ni-based superalloys in exhaust and e-powertrain systems.
Hybrid solutions: HEA-based composites and gradient materials tailored for multifunctionality.

6) Unique Insights

Surface-first adoption: The fastest route to industry implementation lies in HEA coatings, which avoid the need for bulk material qualification.
Metastability as a design tool: Controlling stacking fault energy (SFE) allows activation of deformation mechanisms that enhance toughness.
Integration with data science: Machine learning models, combined with CALPHAD simulations, enable rapid prediction of HEA phase stability and mechanical properties.
Sustainability factor: Future HEA design must prioritize Co- and Nb-free compositions to ensure cost-effectiveness and sustainability.

7) Latest Research

Lightweight HEAs: New Al-Mg systems achieving densities below 6 g/cm³ with corrosion resistance comparable to aluminium alloys.
3D Printing of HEAs: Optimized process maps for microstructural control, with enhanced hardness and wear resistance demonstrated in LPBF-built HEAs.
Refractory HEAs: Nb-Ta-Ti-Hf alloys showing superior creep resistance at 1100–1200 °C.
Hydrogen Embrittlement Studies: Cantor alloy shows delayed hydrogen-induced cracking compared to steels.
Machine Learning Models: Deep learning integrated with CALPHAD predicts stacking fault energy and creep strength with high accuracy, accelerating alloy discovery.

HEAs display a revolutionary approach to alloy design. Their unique chemistry, exceptional properties, and manufacturing flexibility position them as a strong candidate for next-generation automotive and aerospace applications. While challenges like cost, oxidation resistance, and large-scale qualification remain, the trajectory of research suggests that HEAs are steadily moving from the lab to real-world components.

With respect to automobile industry, HEA coatings provide the most immediate opportunities, especially in wear-critical and emission-sensitive parts, whereas lightweight and refractory HEAs are on the path to transform the future of transportation.