Effect of Mo on the Mechanical and Corrosion Behaviors in Non-Equal Molar AlCrFeMnNi BCC High-Entropy Alloys

Co-free body-centered cubic (bcc) high-entropy alloys (HEAs) are prepared, and the elevated mechanical property and corrosion property of the Al0.4CrFe1.5MnNi0.5Mox (x = 0 and 0.1) alloys are studied. The Vickers hardness (HV) of the as-homogenized state is between HV 350 and HV 400. Both alloys are provided with nano-scale NiAl-rich B2 precipitates which contribute to the strength at high-temperature. In addition, adding Mo in the present alloy strengthens by σ phase. Al0.4CrFe1.5MnNi0.5Mo0.1 exhibited outstanding tensile properties, with a yield strength of 413 MPa and ultimate tensile strength of 430 MPa in the elevated tensile test at 600 °C, which is better than that of Al0.4CrFe1.5MnNi0.5 alloy. Through potentiodynamic polarization testing in 0.5 M H2SO4 solution and electrochemical impedance spectroscopy (EIS), it is shown that adding Mo can effectively reduce the corrosion current density and improve the impedance of passive film, since the passivation layer is formed and stable.