The equiatomic high-entropy alloy (HEA) CoCrFeMnNi not only has excellent mechanical properties but also good irradiation resistance. However, the mechanical properties of some equiatomic medium-entropy alloys (MEAs) are superior to those of CoCrFeMnNi HEA. In this study, the irradiation resistance and changes in composition due to irradiation in CoCrNi and CoCrFeNi MEAs and CoCrFeMnNi HEA are investigated. Thin film samples of the MEAs and HEA and Ni used for comparison were irradiated with up to 1.7 × 10¹⁹ ions/m² of 2.4 MeV Cu ions at 673 and 873 K. The average damage in the observed area was 1 displacement per atom (dpa). No voids were observed in any of the MEA and HEA samples even after irradiation at 873 K; however, large voids were formed in Ni irradiated at 873 K. This indicates that the irradiation resistance of CoCrNi and CoCrFeNi MEAs and CoCrFeMnNi HEA was better than that of Ni. In addition, the formation of stacking fault tetrahedra (SFTs), a type of vacancy cluster, at 873 K was much more pronounced in CoCrNi and CoCrFeNi MEAs than in CoCrFeMnNi HEA. Therefore, the irradiation resistance of CoCrNi and CoCrFeNi MEAs is lower than that of CoCrFeMnNi HEA. Moreover, significant Cr segregation occurred in the CoCrNi and CoCrFeNi MEA samples irradiated at 873 K. In contrast, no segregation occurred in CoCrFeMnNi HEA. First-principles calculation results show that the formation rate of Cr-dumbbells is higher in CoCrNi and CoCrFeNi MEAs than in CoCrFeMnNi HEA, and that Cr interstitials are more stable in the MEAs. Therefore, Cr segregation is more likely to occur in the MEAs. Element segregation may affect the irradiation resistance of the alloys.

等原子高熵合金（HEA）CoCrFeMnNi不仅具有优异的力学性能，而且具有良好的抗辐照性。然而，一些等原子中熵合金（MEAs）的力学性能优于CoCrFeMnNi HEA。在这项研究中，研究了 CoCrNi 和 CoCrFeNi MEA 和 CoCrFeMnNi HEA 中的辐照电阻和因辐照引起的成分变化。用于比较的 MEA 和 HEA 和 Ni 的薄膜样品用高达 1.7 × 10 ¹⁹离子/m^{​​ 2进行辐照}在 673 和 873 K 时为 2.4 MeV Cu 离子。观察区域的平均损伤为每原子 1 个位移 (dpa)。即使在 873 K 照射后，在任何 MEA 和 HEA 样品中都没有观察到空隙；然而，在 873 K 辐照的 Ni 中形成了大的空隙。这表明 CoCrNi 和 CoCrFeNi MEA 和 CoCrFeMnNi HEA 的抗辐照性优于 Ni。此外，堆垛层错四面体 (SFTs)（一种空位簇）在 873 K 时在 CoCrNi 和 CoCrFeNi MEA 中的形成比在 CoCrFeMnNi HEA 中更明显。因此，CoCrNi 和 CoCrFeNi MEA 的耐辐照性低于 CoCrFeMnNi HEA。此外，在 873 K 辐照的 CoCrNi 和 CoCrFeNi MEA 样品中发生了显着的 Cr 偏析。相比之下，在 CoCrFeMnNi HEA 中没有发生偏析。第一性原理计算结果表明，CoCrNi和CoCrFeNi MEAs中Cr-dumbbells的形成率高于CoCrFeMnNi HEA，并且Cr间隙在MEAs中更稳定。因此，在 MEA 中更容易发生 Cr 偏析。元素偏析会影响合金的耐辐照性。