Effects of Al Addition on Microstructure and Electrochemical Property of FeCoCrNiMn High-Entropy Alloy in Different Treatment States

FeCoCrNiMn and Al_0.3FeCoCrNiMn high-entropy alloys were prepared by vacuum melting technique, and then subjected to homogenization treatment at 1 150℃ for 6 h (solid solution state) and severe rolling at room temperature followed by annealing at 800℃ for 1 h (rolled and annealed state). The microstructure and the electrochemical property in 0.5 mol·L^-1 H₂SO₄ solution at room temperature of the alloys in solid solution state and in rolled and annealed state were studied. The results show that the two high-entropy alloys in solid solution state were both composed of single face-centered cubic phase. After severe rolling and annealing treatment, FeCoCrNiMn high-entropy alloy was still composed of single face-centered cubic phase, and the grains were refined to 4.57 μm; with the addition of Al, a large amount of σ phase (Cr-rich) and body-centerd cubic phase (Cr-depleted) precipitated in the alloy, and the grains were refined to lower than 500 nm. In the H₂SO₄ solution, the two high-entropy alloys in different treatment states possessed a passive region, and the addition of Al decreased corrosion resistance of the FeCoCrNiMn alloy.