Micro Arc Oxidation of Al-4Si, Al-4Mn and Al-4Mg Binary Alloys

Abstract

Binary synthetic aluminum alloys Al-M (M = Mg, Mn, Si) containing 4 at.% alloying elements as substrate materials were prepared under controlled vacuum/argon atmosphere. The substrates were coated by micro arc oxidation (MAO) method for 120 minutes in aqueous alkaline electrolyte using the same electrical parameters. The phase constituents, chemical composition, surface roughness and the microstructure of the coatings were characterized by XRD, profilometry and SEM-EDS. The average coating thicknesses are 127 mu m, 91 mu m and 78 mu m on Al-4Mn, Al-4Mg and Al-4Si alloys, respectively. All MAO coatings were composed of mullite (3Al(2)O(3)center dot 2SiO(2)) and gamma-Al2O3 phases. In addition to these phases, alpha-Al2O3 phase, in the form of precipitates, was detected in coatings on Al-4Mn and Al-4Mg alloys. The presence of Si, Mn and Mg was detected in the coatings, depending of the chemical content of the substrate alloys.