The study on the magnetic FeCoNiCuAl high-entropy alloy film with excellent corrosion resistance.

FeCoNiCuAl high-entropy alloy films (HEAFs) were prepared by direct current magnetron sputtering. The magnetic properties, corrosion resistance in 3.5 wt% NaCl solution and microstructure of the as-deposited and annealed HEAFs were investigated. The results indicated that the as-deposited HEAFs had an amorphous structure. With the increase of annealing temperature, the HEAFs gradually crystallized and the coercivity increased. The as-deposited HEAF had better corrosion resistance than the bulk FeCoNiCuAl high-entropy alloy (HEA), and the I corr value was 1.41 × 10−6A/cm2. The improved corrosion performance is mainly due to the homogeneity of the composition. After annealing, (Cu, Ni)-rich precipitates appeared in the HEAFs, and the quantity and size of the precipitates increased with increasing annealing temperature. Annealing treatment significantly enhanced the corrosion resistance of the HEAFs. After annealing at 673 K, the optimal I corr of HEAF was 2.74 × 10−7 A/cm2, which was better than the 304 stainless steel, FeSiB amorphous alloy, some HEAFs, etc. The mechanism of corrosion resistance improvement of the HEAFs after annealing treatment was discussed using scanning electron microscopy and X-ray photoelectron spectroscopy. Good corrosion resistance results from high valence oxides and stable passivation films. This work not only provides direction for the enhancement of corrosion resistance of HEA magnetic films, but also provides candidate materials for magnetic film sensors in harsh environments. [Display omitted] • Magnetic FeCoNiCuAl amorphous high-entropy alloy films were prepared. • The as-deposited showed better corrosion resistance than the bulk FeCoNiCuAl HEA. • The annealing treatment significantly improve the corrosion resistance of the films. [ABSTRACT FROM AUTHOR]