Design of lightweight eutectic high-entropy alloy with high strength and thermal stability for high-temperature applications

Eutectic high-entropy alloys (EHEAs), which combine the characteristics of high-entropy alloys (HEAs) and eutectic alloy systems, have emerged as attractive candidates for elevated-temperature applications. Despite this promise, most existing EHEAs still possess relatively high densities and show limited strength stability at high temperatures, constraining their application. In this study, we develop lightweight, thermally stable, and ultrastrong EHEAs by incorporating a robust Heusler-type ordered phase (L2₁ phase) enriched with low-density constituents and by tailoring a eutectic interface with minimal lattice misfit. The lattice misfit between L2₁ and body-centered-cubic (BCC) is quantitatively evaluated to be ∼ 0.27%. This design concept promotes the formation of refined and stable lamellar microstructures accompanied by numerous coherent nanoprecipitates. Using this strategy, we designed a new family of bulk EHEAs Ni₃₅Al₁₆Ti₁₇Cr₁₇V₁₅, Ni₃₄Al₁₆Ti₁₇Cr₁₈V₁₅, and Ni₃₄Al₁₇Ti₁₇Cr₁₈V₁₄ comprising L2₁ and BCC phases. Among these, Ni₃₄Al₁₆Ti₁₇Cr₁₈V₁₅ demonstrates a low density (∼ 6.3 g/cm³) together with outstanding mechanical performance, achieving a yield strength of 1714.57 MPa and a fracture strain of 18%. Its specific yield strength reaches 235.36 MPa·cm³ ·g⁻¹ at 600°C. These results highlight the strong potential of this EHEA system for advanced high-temperature structural applications.