A series of fine-grained FeCoNi(CuAl)_x (x = 0, 0.4, 0.6, 0.8, 1.0) medium-entropy alloy (MEA) and high-entropy alloys (HEAs) were fabricated by Mechanical Alloying (MA) and Spark Plasma Sintering (SPS). The effect of Al and Cu content (x) on phase composition, microstructure, and mechanical properties of the alloys was investigated. Experimental results show that the crystal structure of FeCoNi(CuAl)_x alloy transforms from single (face-centered cubic) FCC phase for x = 0 to FCC + BCC duplex phases for x = 0.4∼1.0, with the fraction of (body-centered cubic) BCC phase gradually increasing with the increase of x. Adding a low content of Al and Cu elements to FeCoNi alloy can significantly hinder the grain growth during sintering process, the average grain size of FCC phase decreases from 0.95 to 0.30 µm at x = 0.4. However, the grain sizes of FCC and BCC phases gradually grow up when x increases from 0.4 to 1.0. The variation in grain size indicates that the atomic diffusion rate of sintered alloy may be influenced by the sluggish diffusion effect in HEA as well as the content of Al and Cu with lower melting points. Mechanical properties of the HEAs are mainly affected by the volume fraction of BCC phase. The compressive yield strength and hardness of HEAs are improved at first and then slightly reduced, while the plasticity drops down continuously with the increase of x. The bulky HEA achieved excellent comprehensive mechanical properties with a compressive yield strength of 1,467.7 MPa and plastic strain to failure of 24.9% at x = 0.6, due to the fine duplex microstructure.

通过机械合金化（MA）和电火花等离子体制造了一系列细晶粒的FeCoNi（CuAl）_x（x = 0、0.4、0.6、0.8、1.0）中熵合金（MEA）和高熵合金（HEA）烧结（SPS）。研究了Al和Cu含量（x）对合金的相组成，显微组织和力学性能的影响。实验结果表明，FeCoNi（CuAl）_x的晶体结构合金从x = 0的单一（面心立方）FCC相转变为x = 0.4〜1.0的FCC + BCC双相相，随着（x）的增加（体心立方）BCC相的比例逐渐增加。在FeCoNi合金中添加低含量的Al和Cu元素会显着阻碍烧结过程中的晶粒长大，在x = 0.4时，FCC相的平均晶粒尺寸从0.95降至0.30 µm。但是，当x从0.4增加到1.0时，FCC和BCC相的晶粒尺寸逐渐增大。晶粒尺寸的变化表明，烧结合金的原子扩散速率可能受到HEA中缓慢的扩散效应以及熔点较低的Al和Cu含量的影响。HEA的机械性能主要受BCC相体积分数的影响。HEA的压缩屈服强度和硬度先得到改善，然后略有降低，而塑性随着x的增加而连续下降。庞大的HEA获得了优异的综合机械性能，由于精细的双相微观结构，在x = 0.6时的压缩屈服强度为1,467.7 MPa，塑性应变破坏率为24.9％。