Effect of processing parameters on the structural and mechanical properties of micro arc oxidized aluminium alloy

The micro arc oxidation process (MAO) was applied to a 2024 ingot aluminium alloy by an AC MAO equipment using an alkali based electrolyte. The processing parameters of the process were positive and negative voltage pulse durations. Structural and morphological characterization of the coating were made by a scanning electron microscope (SEM), an X-ray diffractometer (XRD), a surface profilometer and a thickness gage operating according to the Eddy current principle. Cross sectional hardness of the coatings was measured, and reciprocating wear and immersion corrosion tests were performed. XRD analysis showed that an oxide layer comprising α- and γ-Al₂O ₃ phases was produced on the surface, whose thickness and surface roughness varied by the processing parameters applied. Wear and corrosion resistance of the original alloy significantly improved upon the MAO process. Variation of hardness, wear and corrosion resistance with respect to the processing parameters was discussed based on the experimental data obtained.