In the present study, a series of AlCoCr_xFeNi_2.1 (x = 0, 0.25, 0.5, 0.75, 1.0) eutectic high entropy alloys (EHEAs) have been designed and prepared. And the effect of Cr content on the microstructures and mechanical properties of the AlCoCr_xFeNi_2.1 alloys was systematically investigated. The results indicate that the AlCoCr_xFeNi_2.1 (x > 0) alloys exhibit almost complete lamellar eutectic microstructures with a mixture structure of FCC and B2 phases. And the AlCoFeNi_2.1 alloy without Cr element exhibited a hypoeutectic microstructure with a primary B2 phase. In addition, the eutectic microstructures for AlCoCr_xFeNi_2.1 eutectic alloys do not change significantly. The room temperature compressive tests results show that with an increase in Cr content (from x = 0 to x = 1.0), the yield strength will first decrease, and thereafter increase. The trend is the opposite with the fracture strength and plastic strain. They show an increase trend at first, and then decrease. The AlCoCr_0.5FeNi_2.1 (Cr0.5) alloy shows the best comprehensive mechanical properties. The tensile yield strength, fracture strength, and elongation are 536.5 MPa, 1062 MPa, and 13.8%, respectively. Furthermore, the Cr0.5 alloy also displays a high strength with a yield strength of 362 MPa at 700 ºC. In summary, by changing the Cr content, AlCoCr_xFeNi_2.1 eutectic high entropy alloys with excellent comprehensive mechanical properties were obtained and prepared.

在本研究中， 设计并制备了一系列 AlCoCr _x FeNi _2.1 ( x = 0, 0.25, 0.5, 0.75, 1.0) 共晶高熵合金 (EHEAs)。并且系统地研究了Cr含量对AlCoCr _x FeNi _2.1合金的显微组织和力学性能的影响。结果表明，AlCoCr _x FeNi _2.1 ( x  > 0) 合金表现出几乎完全的层状共晶显微组织，具有 FCC 和 B2 相的混合结构。和 AlCoFeNi _2.1不含 Cr 元素的合金表现出亚共晶显微组织，初生 B2 相。此外，AlCoCr _x FeNi _2.1共晶合金的共晶组织没有显着变化。室温抗压试验结果表明，随着Cr含量的增加（从x  =0到x  =1.0），屈服强度先下降，后上升。断裂强度和塑性应变的趋势相反。它们先呈上升趋势，然后呈下降趋势。AlCoCr _0.5 FeNi _2.1(Cr0.5)合金表现出最好的综合力学性能。拉伸屈服强度、断裂强度和伸长率分别为 536.5 MPa、1062 MPa 和 13.8%。此外，Cr0.5 合金还显示出高强度，在 700 ºC 下的屈服强度为 362 MPa。综上所述，通过改变Cr含量，获得并制备了具有优异综合力学性能的AlCoCr _x FeNi _2.1共晶高熵合金。