Phase evolution, mechanical properties, and corrosion resistance of Ti2NbVAl0.3Zrx lightweight refractory high-entropy alloys

Abstract

Herein, a series of Ti2NbVAl0.3Zrx (x = 0.25, 0.5, 0.75, 1) light refractory high entropy alloys were designed and prepared based on the concept of B2 ordering and solid solution strengthening. The Zr0.25, Zr0.5, and Zr0.75 alloys exhibited a disordered BCC + ordered B2 duplex structure, while the Zr1 alloy displayed a BCC single-phase structure. The addition of Zr hinders the formation of B2 ordering, transforming the alloy from a BCC + B2 duplex structure to a BCC single-phase structure. The Zr0.75 alloy has a yield strength of 1022 MPa and a tensile strain of ∼9.4 %. Furthermore, electrochemical tests were conducted in 3.5 wt% NaCl solution revealed that the Ti2NbVAl0.3Zrx LRHEAs showed high resistance to pitting corrosion. Incorporating the Zr element enhanced the polarization resistance and reduced the corrosion rate; however, excessive Zr content led to a shift in micro-galvanic corrosion from the nanoscale to the microscale, resulting in pitting corrosion. The passivation film compositions of the four alloys formed at a potential of 0.7 VSCE were analyzed by X-ray photoelectron spectroscopy, and their corrosion resistance in a chlorine-containing environment was examined in depth.