SiCp/Al复合材料微弧氧化膜层的生长及耐蚀性

Growth behavior and corrosion resistance of micro-arc oxidation film on SiCp/Al matrix composites

  • 摘要: 在铝酸盐电解液体系中制备了SiCp/Al复合材料的微弧氧化膜层。通过分析微弧氧化过程中电流密度及温度的变化、膜层形貌、膜层与基体界面结构及物相,研究SiCp/Al复合材料表面微弧氧化膜层的生长。利用动电位极化曲线及电化学阻抗谱分析了膜层的耐蚀性。结果表明:微弧氧化初期,SiCp/Al复合材料的Al基体及SiC颗粒与Al界面处优先成膜;并通过薄弱部位不断的击穿放电及熔融物的反复聚集、凝固,实现膜层的稳定生长。随氧化时间延长,膜层厚度增大,生长方式为向内和向外生长,并以向外生长为主。SiCp/Al复合材料基体与膜层界面包括3种结构,主要为界面处靠近Al基体的由Al和O形成的非晶氧化物结构、靠近SiC颗粒的由Si和O形成的致密无微孔的非晶氧化物结构以及有较多微纳米孔的结构。微弧氧化膜层能有效改善SiCp/Al复合材料耐蚀性,浸泡168 h后,微弧氧化膜层的腐蚀电位为−1.212 V,腐蚀电流密度为2.767×10−5 A·cm−2,耐蚀性仍优于基体。

     

    Abstract: The micro-arc oxidation film was fabricated on SiCp/Al matrix composites in an aluminate electrolyte. The growth behavior of micro-arc oxidation film on the surface of SiCp/Al matrix composites was studied by analyzing the changes of current density and temperature, film morphology, interfacial structure and phase. The corrosion resistance of the film was analyzed by potentiodynamic polarization curve and electrochemical impedance spectroscopy. The results show that the film is preferentially formed in the Al substrate and the interface between SiC particles and Al of SiCp/Al matrix composites at the initial stage of micro-arc oxidation. The stable growth of the film is realized through the continuous breakdown and discharge of the weak part and the repeated aggregation. The growth mode is inward and outward growth, and mainly outward growth. The interface between the substrate and the film of SiCp/Al matrix composite consists of three kinds of structures, which are the amorphous oxide structure formed by Al and O near the Al substrate at the interface, the dense amorphous oxide structure formed by Si and O near the SiC particles, and there are many micro and nanoporous structure. The corrosion resistance of SiCp/Al matrix composite can be improved effectively by micro-arc oxidation film. After soaking for 168 h, the corrosion potential of the film is −1.212 V, the corrosion current density is 2.767×10−5 A·cm−2, and the corrosion resistance of the film is still better than that of the substrate.

     

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