Study on Microstructure of the Matrix/Dense Inner Layer Interface in Micro-Arc Oxidizing on Magnesium Alloys

Abstract:

An extensive study was made of the boundary area microstructure between the matrix and dense inner sublayers of the ceramic coating formed on AZ91 magnesium alloy substrate by micro-arc oxidation(MAO).The coating was prepared in an alkaline electrolytic solution composed of 5-20g/l of NaH₂PO₄, 1-5g/l of NaOH, 5-8g/l of KF; 0.5-2g/l of Na₃C₆H₅O₇, and 0.5-2g/l of EDTA , employing a constant-current controlled AC power supply with a current density of 10-30A/dm²; and the microstructure of the coatings was characterized using transmission electron microscopy(TEM) and scanning electron microscopy(SEM). It was found that (1) the main constituent of the coating adjacent to the boundary was microcrystalline and nanocrystalline; (2) the microhardness of the coating adjacent to the boundary was improved than that of the matrix. It was due to the formation of the intermixing of Mg and MgO and their grains were refined, these leaded to fine-crystal strengthen.

• Periodical: Advanced Materials Research (Volumes 1120-1121)
• Pages: 715-722
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.1120-1121.715
• Online since: July 2015
• Authors: Xian Ming Chen*, Qing Lin Pan
• Keywords: Boundary, Coating, Magnesium Alloy, Micro-Arc Oxidation, Microcrystalline, Performance

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