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 CoCrFeNiHf_0.42. At room temperature, CoCrFeNiHfx alloys exhibit increased yield stresses accompanied by the degradation of ductility as raising the Hf content. CoCrFeNiHf_0.1 and CoCrFeNiHf_0.2 show strain hardening rates >2500 MPa at strain <0.3 and high strengths of ~3000 MPa at the strain of 0.5. At the high temperature of 800 °C, the alloy featuring a typical eutectic microstructure exhibits the maximum yield strength of 536 MPa compared to hypoeutectic and hypereutectic compositions. Nevertheless, as-cast eutectic and hypereutectic alloys show severe microstructural instability at 800 °C, as evidenced by the transformation of the eutectic microstructure from lamella to irregular morphology with significant coarsening.

 本文研究了添加不同Hf的CoCrFeNiHf x（x = 0.1-0.6）高熵合金。随着Hf含量的增加，合金的微观结构逐渐从次共晶型转变为过共晶型，FCC枝晶或Laves相为主要相。合金的共晶组成被确定为接近CoCrFeNiHf _0.42。在室温下，CoCrFeNiHf x合金表现出增加的屈服应力，并伴随着Hf含量的增加而延展性降低。CoCrFeNiHf _0.1和CoCrFeNiHf _0.2应变<0.3时，应变硬化率> 2500 MPa，应变0.5时，高强度约为3000 MPa。在800°C的高温下，具有典型共晶微观结构的合金与次共晶和过共晶成分相比，具有536 MPa的最大屈服强度。然而，铸态共晶和过共晶合金在800°C时表现出严重的显微组织不稳定性，这是由共晶显微组织从薄片转变为具有明显粗化的不规则形态所证明的。