Single-phase FeMnNiAl compositionally complex alloy

FeMnNiAl, a compositionally complex alloy, in close to having an equimolar composition, was prepared in bulk and thin-film forms. Arc melting under argon was used for bulk form preparation. The thin-film alloy was produced by Ion Beam Sputter Deposition on a silicon substrate at 620 K. X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to assess the material crystallinity. Both alloy forms display a single-phase and are in crystalline state. The material has a BCC lattice with the lattice constant at 4.08 Å. Dark field TEM image reveals material nanotexturing. The potentiodynamic polarisation in 0.6 moles NaCl and H₂SO₄ shows that open circuit potential (against saturated calomel electrode) at room temperature is approximately - 0.21 V. The alloy is demonstrated to be nobler than 304 SS (by approximately 0.1 V) and develops passivation layer in the corrosive solutions. Nanoindentation test shows that FeMnNiAl alloy thin film has high hardness at 11.7 GPa. It is anticipated that high hardness combined with the passivation ability can make the FeMnNiAl alloy coating a viable candidate for protection of metallic constructions in erosive environments.