Effect of Boron Content on the Microstructure and Properties of FeCoNiCr _0.8 Al _0.2 High‐Entropy Alloys

Balancing strength and ductility in face‐centered‐cubic (FCC) high‐entropy alloys remains a critical challenge. Here, boron microalloying is employed to tailor the microstructure of FeCoNiCr0.8Al0.2 alloys. All alloys retain an FCC matrix, while Cr 2 B precipitates at x ≥ 0.4, refining grains from 90–120 to ∼49.86 μm. Strengthening arises from the combined effects of interstitial solid solution, grain refinement, and Cr 2 B precipitation. The B0.8 alloy exhibits an optimized strength–ductility balance, with a yield strength of 610 MPa, tensile strength of 895 MPa, and elongation of 51%. This behavior is attributed to a semicontinuous Cr 2 B network that strengthens grain boundaries while maintaining matrix deformability. Excessive boron leads to embrittlement. In addition, boron improves wear resistance. These results demonstrate that controlled boron addition is an effective strategy for tuning the strength–ductility trade‐off in FCC high‐entropy alloys, highlighting the critical role of microstructural balance between strengthening phases and matrix plasticity.