Structure, Mechanical Properties, and Corrosion Resistance of the CrCuFeNiMo0.3 High-Entropy Alloy Prepared by Powder Metallurgy

Powder metallurgy methods were used in this study to prepare the CrCuFeNiMo0.3 high-entropy alloy. The alloy’s microstructure, hardness, compression, and corrosion resistance were examined by means of field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction analysis (XRD), as well as employing micro Vickers hardness tester, materials testing machine, and electrochemical workstation. The experimental results revealed light- and dark-colored areas in the alloy's microstructure. The edge of light color was petal-like. Also, alternating stripes were observed in the light-colored area of the microstructure. The EDS and the element surface distribution analysis of the CrCuFeNiMo0.3 alloy revealed the tendency of the elements to segregate. The distribution of chromium, iron and nickel elements is more uniform, while copper elements were enriched in intergranular position, with molybdenum tending to segregation the most. The reason is that the melting point of molybdenum is the highest in the studied CrCuFeNiMo0.3 high-entropy alloy. During sintering, the internal and edge parts of the pressed cylindrical samples were unevenly heated on the micro-level, leading to the irregular diffusion of atoms and facilitating segregation. The segregation of copper elements largely relates to the mixing enthalpy between elements. The mixing enthalpy of the studied CrCuFeNiMo0.3 high-entropy alloy with five principal components is larger than that of intermetallic compounds. It forms simple FCC and BCC structures, inhibiting the emergence of brittle intermetallic compounds. Solution strengthening effect and grain refining effect of molybdenum increase the alloy’s hardness and strength. The highest microhardness value of the alloy was 766 HV, and the compressive strength amounted to approximately 1782 MPa. The fracture mechanism is a quasi-cleavage fracture. The corrosion current density of the alloy in 3.5% NaCl solution is 5.35 ⋅ 10–6 mA/cm2, and the corrosion potential is –0.52 V. Also, the corrosion of the alloy surface is slight, without pitting, and is mainly concentrated in the grain boundary and some light-colored structures.