Nb-induced lattice changes to enhance corrosion resistance of Al0.5Ti3Zr0.5NbxMo0.2 high-entropy alloys
Xudong Yu, Qingjun Chen, Xia Cui, Delai Ouyang
Abstract
Abstract In this work, the effect of lattice structure on the corrosion behavior and passivation film properties of reinforced Al 0.5 Ti 3 Zr 0.5 Nb x Mo 0.2 (x = 0.5,0.8,1) high-entropy alloys are investigated. A single-phase BCC Al 0.5 Ti 3 Zr 0.5 Nb x Mo 0.2 (x = 0.5, 0.8, 1) high-entropy alloys, exhibiting good corrosion resistance, are synthesized using vacuum arc melting. Nb improves the corrosion resistance of high-entropy alloys in two main ways. On the one hand, the alloys show preferential corrosion at the {011} crystalline planes. Increasing Nb content reduced the {011} crystalline plane spacing, enhancing the corrosion resistance of Al 0.5 Ti 3 Zr 0.5 NbMo 0.2 . On the other hand, during the corrosion process, Nb, which has a large atomic radius and strong oxygenophilicity, interacts with each metal element, contributing to the uphill diffusion of Al/Ti and the downhill diffusion of O. The low-valent oxides form first continuously react with the inward-diffusing O to form high-valent oxides. This results in the formation of a layered passivation film with high breakdown potential and high stability. This work provides a basis for designing chemically robust alloys for extreme environments.