Conventional alloys are built around one dominant metal (iron in steel, aluminium in aero-alloys). High-entropy alloys (HEAs) break this rule: they mix five or more principal elements in near-equal proportions. The high configurational entropy stabilises simple solid-solution phases, yielding remarkable strength, ductility, and corrosion and high-temperature resistance. Additive manufacturing (AM) is an ideal way to make them.
Working principle
In laser powder-bed fusion (LPBF), a laser melts powder layer by layer. The extremely high cooling rates (10⁵–10⁶ K/s) cause rapid solidification, which refines the microstructure, suppresses segregation and can produce metastable phases unattainable by casting. For HEAs this means fine grains and excellent mechanical properties straight from the build, plus the geometric freedom of AM.
| Property | Conventional alloy | High-entropy alloy |
|---|---|---|
| Composition | One base + minor elements | 5+ near-equal elements |
| Phase | Base + intermetallics | Stable solid solution |
| Strength–ductility | Often a trade-off | Can have both |
| High-temp stability | Limited | Excellent |
ChallengeAM's rapid cooling is a double-edged sword: it refines structure and strengthens HEAs, but the steep thermal gradients cause residual stress and cracking that must be controlled with parameter and scan-strategy tuning.
Applications
- High-temperature turbine and aerospace components
- Wear- and corrosion-resistant tooling and coatings
- Cryogenic structures exploiting HEA toughness
References & further reading
- Yeh et al., “Nanostructured High-Entropy Alloys with Multiple Principal Elements,” Adv. Eng. Mater., 2004.
- George et al., “High-entropy alloys,” Nature Reviews Materials, 2019.
- Li et al., “Selective laser melting of high-entropy alloys: a review,” Additive Manufacturing, 2020.