Designing FeCr0.7NiCu0.5Ti0.5 high-entropy alloy doped with rare earth yttrium: Effects on microstructure and passive film

After constant potential passivation (CPP), the effect of rare earth yttrium (Y) on the corrosion resistance of the passive film on the surface of FeCr0.7NiCu0.5Ti0.5 alloy in H2SO4 was investigated. The results manifested that when Y content exceeded 0.04, the microstructure of Ni3Ti transformed into Cu5Y phase, and gradually expanded with the addition of Y. XPS etching analysis of passive film composition with changing etching depth and cyclic polarization analysis of passive film pitting corrosion sensitivity are two methods used to assess the corrosion resistance of alloy. Compared with FeCr0.7NiCu0.5Ti0.5 alloy and FeCr0.7NiCu0.5Ti0.5Y0.06 alloy, the passivation current density after CPP reduced from 5.682 × 10−3 to 4.630 × 10−4 A/cm2. With the addition of Y, the protection and density of the passive film was enhanced, resulting in an improvement in the corrosion resistance of the alloy. The pitting corrosion behavior was related to the changes in inclusion content and morphology caused by Y, and rare earth was advantageous to boost the passivation capability of FeCr0.7NiCu0.5Ti0.5 series alloy. •The novel FeCrxNiCu0.5Ti0.5Yx (x = 0–1.0) high-entropy alloys are designed.•The doped Y promotes the formation of HCP phase.•The addition of Y can improve the compactness of the passive film.