Microstructures and properties of Crx-FeNiCu0.5Ti0.5 high-entropy alloys for corrosion resistance

In this study, a novel high entropy alloy (HEA) of Crx-FeNiCu0.5Ti0.5 (in mole ratio, x = 0, 0.3, 0.5, 0.7, 0.9 and 1.2) was designed and prepared by arc melting to investigate its microstructure and corrosion resistant behavior. The phase analysis manifested that the microstructures transformed from face-centered cubic (FCC) + intermetallic compounds (IMs) of Cr-free alloy to FCC + IMs + body-centered cubic (BCC) phase with the increase of Cr molar ratio. The potentiodynamic polarization curves indicated that FeCr0.7NiCu0.5Ti0.5 alloy showed good corrosion performance with a corrosion potential of −0.181 V and a self-corrosion current density of 5.455 × 10−7 A/cm2 in 0.5 M H2SO4 solution. The chemical composition from XPS test displayed that Cr2O3, TiO2 and Fe-oxides on the sample surface form different strength passive films, reducing ionic diffusion and improving corrosion resistant, which was the key anti-corrosive mechanism.