Abstract In order to reveal the relationship between microstructure evolution and mechanical properties of CoCrFeMnNi high entropy alloys (HEAs), samples were prepared by directional solidification process with different cooling rates. The solidified phases of CoCrFeMnNi HEA including two different FCC phases, CoCrFeNi3-enriched FCC1 phase and MnNi-enriched FCC2 phase. When the cooling rate increased from 30 × 10−3K/s to 600 × 10−3K/s, the preferred orientation of CoCrFeNi3 transformed from (001) to (101), and the preferred orientation of MnNi transformed from (010) to (110). Meanwhile, the primary dendritic arm spacing decreased from 500 μm to 100 μm, and the secondary dendritic spacing decreased from 120 μm to 10 μm. The yield strength increased from 270 MPa to 428 MPa, and the ultimate tensile strength increased from 392 MPa to 584 MPa. The grain boundary strengthening plays a vital role in the strengthening of directionally solidified CoCrFeMnNi HEA, and the fracture morphology demonstrated the fracture mechanism is ductile fracture.

中文翻译：

---

定向凝固CoCrFeMnNi高熵合金组织演变及力学性能

摘要 为了揭示CoCrFeMnNi高熵合金(HEAs)组织演变与力学性能之间的关系，采用不同冷却速率的定向凝固工艺制备样品。CoCrFeMnNi HEA 的凝固相包括两种不同的 FCC 相，即富含 CoCrFeNi3 的 FCC1 相和富含 MnNi 的 FCC2 相。当冷却速度从30×10-3K/s提高到600×10-3K/s时，CoCrFeNi3的择优取向由(001)转变为(101)，MnNi的择优取向由(010)转变为( 110)。同时，一次枝晶臂间距从 500 μm 减小到 100 μm，二次枝晶间距从 120 μm 减小到 10 μm。屈服强度从270 MPa提高到428 MPa，极限抗拉强度从392 MPa提高到584 MPa。