Microstructural evolution and corrosion behavior of FeCoNiCrVZr high entropy alloys

Abstract

Recently, high entropy alloys (HEAs), a new class of alloys that contains five or more principal elements in equiatomic or near equiatomic proportional ratio (5-35 wt%), have attracted increasing attention because of their unique compositions, microstructures, corrosion behaviour and other adjustable properties. The configuration entropy in the HEAs tends to stabilize the solid solution formation, such as body-centred-cubic (BCC), face-centred-cubic (FCC) and/or hexagonal-closed-pack solid solution. Now, HEAs are considered as a paradigm shift for the next generation high-temperature alloys in the extreme environments, such as aerospace, cutting tools and bearing applications. In this work, microstructure evolution and corrosion behaviour of (Fe25Co25Ni25Cr20V5)100-XZrX (x=0, 2.5, 5, 7.5, 10 at. %) HEAs were studied. The reported HEAs were cast in the high vacuum arc melting cum casting unit under the pure argon gas environment. Using a combination of scanning electron microscopy (SEM), X-ray energy spectroscopy analysis and X-ray Diffraction techniques, three phases were identified in the as-cast conditions: FCC, two mixed solid solutions phases. The microscopic results were consistent with thermodynamic simulations. The effect of Zr on microstructural evolution of HEAs is systematically investigated. The corrosion tests of FeCoNiCrV HEA were performed using potentiodynamic polarisation method in the solutions: pure H2O, Sea Water, 3M NaCl, 3M NaOH and 3M HCl. The developed HEA shows better corrosion resistance property as compared to the conventional IS2062 steel. The results of the corrosion tests were found to be very much in cognizance with the theoretical analysis.