Abstract: In this paper, the effect of Cr element on the phase composition, microstructure, phase evolution of FeNiCuCoCr_x(x=0, 0.5, 1.0, 1.5, 2.0) high-entropy alloy powders and on the high-temperature oxidation resistance and corrosion resistance of bulk high-entropy alloys were systematically investigated. The results show that the high-entropy alloy powders after mechanical alloying are composed of face-centered cubic (FCC) phase and body-centered cubic (BCC) phase. With the increase of Cr content, the strength of the characteristic peak of BCC phase increases. The BCC phase of FeNiCuCoCr_x(x=0, 0.5, 1.0, 1.5, 2.0) high-entropy alloys is dissolved in the matrix during high-temperature sintering, and the FCC phase is decomposed into Cu-rich phase (FCC1 phase) and Cu-deficient phase (FCC2 phase), and the microstructure and composition uniformity of the alloy is high. During the isothermal oxidation process at 900 ℃, the FeNiCuCoCr_0.5 high-entropy alloy forms a continuous and dense oxide film that adheres tightly to the substrate. When the thickness of the film is 25 μm, its high-temperature oxidation resistance is the best. The electrochemical tests results in 3.5% (mass fraction) NaCl solution reveal that the FeNiCuCoCr_0.5 high-entropy alloy exhibits the best corrosion resistance, with a corrosion current density of 5.56×10^-8 A/cm² and a charge transfer resistance of 6 821 Ω·cm². Compared to other FeNiCuCoCr_x(x=0, 1.0, 1.5, 2.0) high-entropy alloys, the corrosion current density is one order of magnitude lower. Compared to other FeNiCuCoCr_x(x=0, 1.0, 1.5, 2.0) high entropy alloys, the transfer resistance of FeNiCuCoCr_0.5 high entropy alloy increases by 51.9%, 18.8%, 233.4% and 265.3%. The research results provide new ideas for the composition design of corrosion-resistant FeNiCuCoCr high-entropy alloys.

Key words: mechanical alloying, phase change, FeNiCuCoCr_x high-entropy alloys, high-temperature oxidation resistance, corrosion resistance