Effects of Directional Solidification Preparation Process on Microstructure and Compressive Properties of CoCrFeNiMn_x High Entropy Alloy

CoCrFeNiMn_x (x=0.25, 0.75) high entropy alloys were prepared by vacuum arc melting and directional solidification, and the effects of directional solidification process on its microstructure evolution and compressive properties were studied. The microstructure of the alloys was observed by optical microscope (OM) and scanning electron microscope(SEM), the phase structure and composition of the alloys were analyzed by X-ray diffractometer (XRD) and energy dispersive spectrometer (EDS), and the compressive properties of the alloy were tested by universal testing machine. The results show that, compared with the alloy prepared by arc melting, the microstructure of the alloy changes from a single FCC₁ structure to a mixed FCC₁+FCC₂ structure after directional solidification. Moreover, the alloys grains grow preferentially, the grain size increases, and the microstructure morphology changes from dendrite to equiaxial dendrite.After directional solidification, the compressive strength of CoCrFeNiMn_0.25 alloy decreases from 1905 MPa to 1810 MPa, and the compressive strain is better.