High-content ductile coherent nanoprecipitates achieve ultrastrong high-entropy alloys

TLDR

Precipitation‑hardening high‑entropy alloys that balance strength and ductility are promising for structural use, yet most rely on near‑equiatomic compositions that limit the formation of intermetallic precipitates that drive strength. This study proposes a phase‑separation strategy that creates a near‑equiatomic matrix in situ while forming strengthening phases, enabling a precipitation‑hardening high‑entropy alloy regardless of the starting atomic ratio. The authors develop a non‑equiatomic alloy that employs spinodal decomposition to generate a low‑misfit coherent nanostructure comprising a near‑equiatomic disordered FCC matrix and high‑content ductile Ni₃Al‑type ordered nanoprecipitates. The resulting spinodal order–disorder nanostructure boosts strength by ~1.5 GPa (>560 %) over a non‑precipitated HEA, achieving a tensile strength of 1.9 GPa—among the highest for bulk HEAs—while maintaining ductility above 9 %.

Abstract

Abstract Precipitation-hardening high-entropy alloys (PH-HEAs) with good strength−ductility balances are a promising candidate for advanced structural applications. However, current HEAs emphasize near-equiatomic initial compositions, which limit the increase of intermetallic precipitates that are closely related to the alloy strength. Here we present a strategy to design ultrastrong HEAs with high-content nanoprecipitates by phase separation, which can generate a near-equiatomic matrix in situ while forming strengthening phases, producing a PH-HEA regardless of the initial atomic ratio. Accordingly, we develop a non-equiatomic alloy that utilizes spinodal decomposition to create a low-misfit coherent nanostructure combining a near-equiatomic disordered face-centered-cubic (FCC) matrix with high-content ductile Ni 3 Al-type ordered nanoprecipitates. We find that this spinodal order–disorder nanostructure contributes to a strength increase of ~1.5 GPa (>560%) relative to the HEA without precipitation, achieving one of the highest tensile strength (1.9 GPa) among all bulk HEAs reported previously while retaining good ductility (>9%).