Microstructures and mechanical properties of CoCrFeNiHfx high-entropy alloys

CoCrFeNiHfx (x = 0.1–0.6) high-entropy alloys with different Hf additions are investigated in this paper. As the Hf content increases, the alloy microstructure gradually transforms from the hypoeutectic type to the hypereutectic type, with primary phases of either FCC dendrites or Laves phases. The eutectic composition of the alloy is identified to be close to CoCrFeNiHf0.42. At room temperature, CoCrFeNiHfx alloys exhibit increased yield stresses accompanied by the degradation of ductility as raising the Hf content. CoCrFeNiHf0.1 and CoCrFeNiHf0.2 show strain hardening rates >2500 MPa at strain