Analysis of Phase Distribution for Ceramic Coatings Formed by Microarc Oxidation on Aluminum Alloy

Abstract

The phase distribution for ceramic coatings formed by microarc oxidation (MAO) on 2024 aluminum alloy was investigated using X‐ray diffraction. The results showed that the ceramic coatings mainly consisted of α‐Al 2 O 3 and γ‐Al 2 O 3 phases. The percentage of α‐Al 2 O 3 gradually increased from the external surface to the interface between the coating and the substrate of samples. The surface layer of coatings mainly contained the γ‐Al 2 O 3 phase, and its fraction of the composition remained almost constant with oxidation time. It is believed that the difference in the amounts of α‐Al 2 O 3 and γ‐Al 2 O 3 phases in the different layers of coatings was caused by the various cooling rates of molten Al 2 O 3 , which temporarily existed in the microarc zone.