Cailiao Baohu (Feb 2024)

Effect of Constant Voltage and Constant Current Interaction Mode on Microstructure and Properties of Micro-Arc Oxidation Ceramic Film on AZ31B Magnesium Alloy

  • SHU Yinfeng, JIANG Bo, WANG Chao, SONG Renguo

DOI
https://doi.org/10.16577/j.issn.1001-1560.2024.0031
Journal volume & issue
Vol. 57, no. 2
pp. 35 – 42

Abstract

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In order to study the effect of the superposition mode of constant voltage and constant current on the microstructure and properties of micro-arc oxidation coatings on AZ31B magnesium alloy，the AZ31B magnesium alloy was used as substrate under the condition of the same electrolyte and electric parameters，and micro-arc oxidation (MAO) ceramic coatings were prepared on AZ31B magnesium alloy by four different power supply working modes: constant current，constant voltage，first constant current and then constant voltage，first constant voltage and then constant current.Subsequently，scanning electron microscopy(SEM)，electrochemical workstation，X-ray diffraction (XRD) and high-temperature friction and wear tester were used to characterize the MAO ceramic coatings on AZ31B magnesium alloy.Results showed that after the substrate was treated with micro-arc oxidation， a micro-arc oxidation ceramic coating was formed on the surface.The peaks of MgO， MgF2 and Mg2SiO4 reinforcement phases of the as-prepared MAO coating under the power mode of first constant current and then constant voltage (0.7 A/6 min＋400 V/4 min) were higher than those under the other modes.In addition， the surface of MAO ceramic coatings was flat， the micropores were small and evenly distributed， the compactness was good， and the coatings was closely combined with the substrate.Compared with the coatings obtained under the other modes， the wear time of the coating prepared under the power mode of first constant current and then constant voltage had the longest wear through time， and the wear resistance of the material was improved.In the comparison of the substrate， the corrosion potential of the coating prepared under the power mode of first constant current and then constant voltage increased from -1.497 4 V to -1.376 9 V， and the corrosion rate was reduced from 0.009 1 mm/a to 0.002 0 mm/a，indicating that the corrosion resistance was significantly improved.

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