Influence of potential on structure and properties of microarc oxidation coating on Mg alloy |
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Authors: | Deng Shu-hao Yi Dan-qing Gong Zhu-qing and Su Yu-chang |
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Affiliation: | (1) School of Materials Science and Engineering, Central South University, 410083 Changsha, China;(2) School of Metallurgical Science and Engineering, Central South University, 410083 Changsha, China |
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Abstract: | In order to obtain optimizing microarc oxidation coating on Mg alloy from a friendly-enviormental electrolyte free of Cr6+ and PO
4
3−
, constant potential regime was applied to produce it. The influence of potential on the morphology, composition, structure
and other properties, such as microhardness and corrosion resistance were investigated by scanning electron microscopy (SEM),
energy dispersive spectroscope (EDS), X-ray diffraction (XRD), hardness tester and electrochemical method. The results clearly
show that oxidation potential plays an important role in the formation of coating’s structure and properties. The microarc
oxidation coating is smooth and white, which consists of two layers. The external layer is loose and porous and enriched in
Al and Si. Moreover, its content of Al and Si increases with the increasing operated potential. While the inner layer is compact
and the content of Al and Si are lower than that of the external layer. The coating is composed of several phases and the
major phases are MgAl2O4 and MgO, and the minor phases are Al2O3 and SiO2 when the potential is higher. The microhardness of coating is obtained the maximum at the potential of 45 V, so does the
corrosion resistance. |
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Keywords: | microarc oxidation magnesium alloy structure property |
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