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

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.