Structure and corrosion in NaCl solution of quasicrystalline Al–Cu–Fe cast alloys and thin films

Abstract

For the first time, quasicrystalline Al₆₀Cu₂₈Fe₁₂ films with 260 nm thickness cooled at 10¹²–10¹⁴ K/s were produced by the modernized method of three-electrode ion-plasma sputtering. Films were deposited on NaCl substrate. The structure of as-sputtered films was investigated in comparison with that of as-cast specimens by methods of quantitative metallography, X-ray analysis, and scanning electron microscopy. Corrosion behavior in 5% NaCl aqueous solution was studied by potentiodynamic method and model tests. In the structure of the as-cast Al–Cu–Fe alloy, the quasicrystalline icosahedral i-phase was established to co-exist with λ -Al₁₃Fe₄ , τ-AlCu(Fe), η-AlCu, and θ-Al₂Cu crystalline phases and occupy ~56 % of the alloy volume. The Al–Cu–Fe film contains dispersive quasicrystalline i-phase (~3 nm in size) that is stable up to 723 К. Corrosion of the as-sputtered Al–Cu–Fe film runs at the lower rate as compared with that of the as-cast alloy of the same composition. Model corrosion tests for 1, 2, 3, 4, 8 days with 5% NaCl solution at 293 K indicate that the investigated Al–Cu–Fe film remains virtually untouched by corrosion. No marks of pittings typical for as-cast Al–Cu–Fe alloys are observed on the film surface affected by saline solution.