Corrosion and wear behaviors of AlCoCr1+xFe1-xNi2.1 high-entropy alloys

Abstract

High-entropy alloys (HEAs) with multiphase structures display an excellent combination of strength and fracture toughness. However, the uneven distribution of the various phase compositions often leads to localized corrosion. In this work, the AlCoCr_1+xFe_1-xNi_2.1 (x = 0.6, 0.8, and 2.0) HEAs are designed using the calculation of phase diagrams (CALPHAD) method and prepared by vacuum arc melting. The results indicate that the AlCoCr_1+xFe_1-xNi_2.1 (x = 0.6, 0.8, and 2.0) HEAs are composed of three phases: face-centered cubic (FCC), body-centered cubic (BCC), and ordered body-centered cubic (B2) phases. BCC phase contains a high concentration of Cr, while B2 phase has a high concentration of Ni and Al. On the other hand, FCC is rich in Cr, Fe, and Co. By increasing the Cr/Fe ratio, the volume fraction of the FCC/B2 lamellar eutectic microstructure decreases, while the volume fraction of the BCC/B2 coherent network microstructure increases. This results in an increase in the corrosion resistance of the HEAs, evidenced by the low values of corrosion current densities and high corrosion potentials. The protective passive film’s formation depends on the Cr and Al content. The Cr-rich coherent nanophases in the Al-rich B2 phase result in a more homogeneous and thicker passive film, which can inhibit the expansion of corrosion pits. And advanced wear resistance counted on appropriate phase fraction, that is, FCC accounted for about 33.56 vol. % and BCC/B2 accounted for 66.44 vol. %. The wear rate of all the HEAs is ∼10^–5 mm³/(N·m), and the oxidation wear and abrasive wear play a dominant role in all the samples. This study provides an attractive strategy for the development of corrosion-resistant and wear-resistant high-entropy alloys.