The Effect of Nb-Content on the Microstructures and Corrosion Properties of CrFeCoNiNb(x) High-Entropy Alloys

This work studied the effect of niobium-content on the microstructures, hardness, and corrosion properties of CrFeCoNiNb(x) alloys. Results indicated that the microstructures of these alloys changed from granular structures (CrFeCoNi alloy) to the hypereutectic structures (CrFeCoNiNb(0.2) and CrFeCoNi(0.4) alloys), and then to the hypoeutectic microstructures (CrFeCoNiNb(0.6) and CrFeCoNi alloys). The lattice constants of the major two phases in these alloys, fcc and Laves phases (hcp), increased with the increasing of Nb-content because of solid-solution strengthening. The hardness of CrFeCoNiNb(x) alloys also had the same tendency. Adding niobium would slightly lessen the corrosion resistance of CrFeCoNiNb(x) alloys in 1 M deaerated sulfuric acid and 1 M deaerated sodium chloride solutions, but the CrFeCoNiNb(x) alloys still had better corrosion resistance in comparison with commercial 304 stainless steel. In these dual-phased CrFeCoNiNb(x) alloys, the fcc phase was more severely corroded than the Laves phase after polarization tests in these two solutions.