不同加压方式下镁合金微弧氧化膜结构及耐蚀性的变化规律

Characteristics of microstructure and corrosion resistant of micro arc coatings on magnesium alloy fabricated with different power loading processes

摘要:

硅酸盐体系电解液中采用恒压、变压两种加压方式对AZ91D镁合金进行不同时间的微弧氧化处理，研究膜层的厚度、表面形貌、物相组成及耐蚀性随时间的变化规律，对膜层中微孔的大小、数量及表面孔隙率进行定量统计，比较两加压方式下膜层的差异。结果表明：两加压方式下，膜层结构随时间的变化规律基本相同，其变化幅度变压方式下相对较大；随着处理时间的增加，膜层的厚度不断增大，微孔数量不断减少，较大微孔不断增多，表面孔隙率不断增大，而物相组成却不变；膜层的耐蚀性恒压方式下不断增强，变压方式下则先增大后减小；与变压方式相比，恒压方式下膜层生长前期的生长速率较大，更有利于工业化生产。

Abstract:

AZ91D magnesium alloys were treated at different time by micro arc oxidation (MAO) in silicate-containing electrolyte. In this work，two types of power loading processes, named P1 mode (constant voltage) and P2 mode (variable voltage ) respectively, were used to prepare the coatings. Varitations of the thickness, surface morphology, phase composition and corrosion resistant of the coatings with treatment time were investigated and the size and amount of the micro pores on coating surface and the surface porosity were studied quantitatively. The results show that the coatings obtained under these two power loading processes had similar evolution patterns in characteristics of microstructure and the extent of which was larger in P2 mode. With prolonging treatment time, the thickness of the coatings was enlarged, with the amount of the total mircro pores and the bigger ones decreasing and increasing, respectively, and the surface porosity of the coatings increased. However, the phase composition of the coatings had no change. The corrosion resistance of the coatings increased continually under P1 mode but it firstly increased and then decreased under P2 mode with treatment time. Comparing these two processes, the P1 mode has an advantage in industrial applications because the MAO coating can grow in a larger rate during the early stage.