Effects of Hybrid Voltages on Oxide Formation on 6061 Al-alloys During Plasma Electrolytic Oxidation |
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Authors: | Kai Wang Bon Heun Koo Chan Gyu Lee Young Joo Kim Sunghun Lee Eungsun Byon |
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Institution: | 1. School of Nano & Advanced Materials Engineering, Changwon National University, Changwon 641-773, Korea;2. Surface Technology Research Center, Korea Institute of Materials Science, Changwon 641-010, Korea |
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Abstract: | Plasma electrolytic oxidation (PEO) is carried out on 6061 Al-alloys in a weak alkaline electrolyte containing NaOH, Na2SiO3 and NaCl. Centered on the correlation of composition and structure, analyses by means of X-ray diffration (XRD), scanning electron microscope (SEM) and energy dispersive spectrometry (EDS) are conducted on the specimens, which have been PEO-treated under hybrid voltages of different direct current (DC) values (140-280 V) with constant alternate current (AC) amplitude (200 V). Attention is paid to the composition, properties and growth mechanism of oxide layers formed with hybrid voltages. Moreover, the main effects of DC value are discussed. Ceramic layers with a double-layer structure which combines hard outer and soft inner layers are found to be consist of α-Al2O3, γ-Al2O3 and mullite. With the DC values increasing, the growth of the ceramic layers tends to have increasingly obvious three-stage feature. |
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Keywords: | plasma electrolytic oxidation oxide layer aluminum alloys alkaline electrolyte hybrid voltages |
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