(Al₂O₃-SiO₂)_sf/AZ91D镁基复合材料微弧氧化膜的制备及电化学阻抗谱分析

来源期刊：金属学报2011年第1期

论文作者：朱庆振 薛文斌 鲁亮 杜建成 刘贯军 李文芳

文章页码：74 - 80

关键词：镁基复合材料； 微弧氧化膜； 电化学阻抗谱 (EIS)

Key words：magnesium matrix composite； microarc oxidation coating； electrochemeical impedance spectroscopy (EIS)

摘    要：在硅酸盐电解液体系中,采用交流微弧氧化方法在增强体体积分数为33%的(Al₂O₃-SiO₂)_sf/AZ91D镁基复合材料表面制备出完整的保护性氧化膜.利用SEM,EDS和XRD分析了氧化膜的形貌、成分和相组成,测量了膜层的显微硬度分布.采用电化学阻抗谱(EIS)评价了微弧氧化表面处理前后复合材料的电化学腐蚀性能,确立了不同浸泡时间对应的等效电路.结果表明,微弧氧化膜主要由MgO和Mg₂SiO₄相组成,最大硬度达到1017 HV.氧化膜电化学阻抗模值|Z|与镁合金基体相比大幅度提高,耐腐蚀性能明显高于基体.在3.5%NaCl溶液里浸泡96 h后,EIS出现感抗弧,显示膜内部开始出现点蚀破坏.氧化膜耐蚀性由膜内致密层特性所决定.

Abstract: A thick protective ceramic coating on 33% (Al₂O₃-SiO₂)_sf/AZ91D (volume fraction) magnesium matrix composite was prepared by the microarc oxidation (MAO) technique in silicate electrolyte. SEM, EDS and XRD were employed to analyze the surface morphology, composition and phase constituent of the coating, furthermore, the microhardness profile of the coating was also measured. The electrochemical corrosion properties of magnesium matrix composite before and after the MAO surface treatment were evaluated by electrochemical impedance spectroscopy (EIS), and the equivalent circuits corresponding to different immersion times were suggested. The results show that the fiber-reinforced composite surface is completely covered by the MAO coating. The ceramic coating mainly consists of MgO and Mg₂SiO₄ phases. The maximum microhardness of coating is up to 1017 HV. The electrochemical impedance modulus, |Z|, of the coated magnesium matrix composite increases significantly compared with bare composite, thus the magnesium matrix composite coated by MAO displays a good corrosion resistance. The occurrence of inductive loop in EIS of coated composite after 96 h immersion in 3.5% NaCl solution implies the pitting deterioration in the coating. The corrosion resistance of coated magnesium matrix composite is determined by the properties of inner compact layer of MAO coating.