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董海荣,马颖,王晟,安凌云,郝远.氟化钾对AZ91D镁合金微弧氧化膜的生长及微观结构的影响[J].稀有金属材料与工程(英文),2018,47(1):249~254.[DONG Hairong,MA Ying,WANG Sheng,AN Lingyun,HAO Yuan.Effect of potassium fluoride on growth and microstructure of MAO coatings on AZ91D magnesium alloys[J].Rare Metal Materials and Engineering,2018,47(1):249~254.]
Effect of potassium fluoride on growth and microstructure of MAO coatings on AZ91D magnesium alloys
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Received:November 20, 2015  Revised:May 04, 2016
DOI:
Key words: AZ91Dmagnesium alloy  micro arc oxidation  potassium fluoride  growth  microstructure
Foundation item:甘肃省创新研究群体计划(1111RJDA011)
Author NameAffiliationE-mail
DONG Hairong Lanzhou University of Technology donghairong011@163.com 
MA Ying Lanzhou University of Technology maying@lut.cn 
WANG Sheng Lanzhou University of Technology  
AN Lingyun Lanzhou University of Technology  
HAO Yuan Lanzhou University of Technology  
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Abstract:
      AZ91D magnesium alloys were processed in the base electrolyte composed with sodium hydroxide and sodium silicate, not containing or containing potassium fluoride respectively, by micro arc oxidation (MAO). Influence of potassium fluoride on growth, microstructure and corrosion resistant of the coatings was investigated. The results show that after potassium fluoride was added to the base electrolyte, the breakdown voltage to the specimen decreased but the breakdown process was more vigorous to lead to formation of larger sparks on the specimen surface during micro arc oxidation. As a result, the grow rate of the coating significantly increased and the obtained coating had a remarkable improvement in terms of coating thickness. Meanwhile, the surface porosity of the coating somewhat increased but the amount of the micro-pores on the coating surface decreased. The addition of potassium fluoride into the electrolyte is helpful for the formation of MgF2and MgAl2O4 phases of the coating. Compared with silicate and oxygen elements from the electrolyte, F- ion is more likely to be adsorbed by magnesium in the substrate and also easily overcomes the obstacle of the generated coating to migrate into the inner of the coating. The corrosion resistance of the coating treated in the electrolyte with potassium fluoride is increased under the influence of significant increasing in coating thickness mainly and the existence of favorable phases such as MgF2 newly born and more MgAl2O4.,