Analyses of microarc oxidation coating formed on AZ91D alloy in phosphate electrolytes

Abstract

This paper studied the appearance transition of microdischarges, the phase composition and the morphology evolution of the oxide film formed by microarc oxidation on AZ91D magnesium alloy. The appearance of microdischarges population experienced apparent changes in size, spatial density and color, which was related with the changes of the type and quantity of the disintegrated gas bubbles generated at the interface between the electrolyte and substrate. Correspondingly, the diameter of micropores together with net-like fine microcracks increased when a higher voltage was employed. The coating was composed of MgO, MgAl₂O₄ and there existed a fluoride-enriched zone of about 3–5 μm at the film/substrate interface.

Keywords

AZ91D alloy / microarc oxidation / microdischarge

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