Eutectic high-entropy alloys (EHEAs) are receiving extensive attention due to their unique physical/chemical properties. However, apart from the face-centered-cubic (FCC) + B2 EHEA system, most other reported EHEA systems gradually lose their advantage for industrial applications due to inherent brittleness during tensile loading at room temperature. Here, a novel combination of spheroidization, cold-rolling, and recrystallization was applied in a brittle CoCrNi2−(V3B2Si)0.2 EHEA to achieve the synergistically improved strength and ductility. A well-designed microstructure with spherical M3B2 embedded at the grain boundaries of fine FCC was obtained. The resulting microstructure markedly increases the ultimate tensile strength, yield strength, and total elongation from 923 MPa, 620 MPa, and 1.3% to 1326–1530 MPa, 990–1330 MPa, and 8.4%–13.9%, increased by 43.7%–65.8%, 59.7%–114.5%, and 546%–969%, respectively. The strengthening and plasticizing mechanisms are mainly attributed to the multiple barriers that hinder dislocation movement and the customized microstructure that results in a uniform stress distribution, respectively. This work provides a new approach for synergistically improving the strength-ductility of brittle EHEAs to meet engineering safety requirements.
