Ultrastrong High‐Ductility Ni35Co35Fe10Al10Ti8B2 High‐Entropy Alloy Strengthened with Super‐High Concentration L12 Precipitates

Abstract

L12 phase hardening alloys with excellent mechanical properties are of great significance for structural applications. However, low volume fractions of L12 precipitates in conventional alloys (nearly lower than 60%) tend to limit their practical usage, while the strengths of the alloys generally increase with L12 precipitation contents. Herein, a novel high‐entropy alloy (HEA) Ni35Co35Fe10Al8Ti10B2 with ultrahigh concentration L12 precipitates is successfully designed aided by the calculation of phase diagrams (CALPHAD). The volume fraction of L12 precipitates in this HEA is up to 75% and outperforms that of most of traditional superalloys. The novel L12‐strengthened Ni35Co35Fe10Al8Ti10B2 has an ultrahigh tensile yield strength of ≈1.45 GPa, ultimate tensile strength of ≈1.9 GPa, and great ductility of ≈23% at room temperature. The desirable strength–ductility combination is superior to most of conventional superalloys and reported HEAs, mainly due to the presence of ultrahigh concentration L12 precipitates that act as dislocation obstacles and the formation of numerous stacking faults and deformation twining. This work is expected to provide guidance for developing new high‐performance HEAs with an excellent combination of strength and ductility.