镁合金微弧氧化膜层结构

来源期刊：中南大学学报(自然科学版)2006年第6期

论文作者：陈显明 罗承萍 刘江文 李文芳

文章页码：1065 - 1069

关键词：镁合金;微弧氧化;微观结构;膜层

Key words：magnesium alloy; micro-arc oxidation; microstructure; ceramic coating layer

摘    要：在硅酸盐碱性溶液中,采用恒电流控制模式,在电流密度为20 A/dm²时,以镁合金AZ91为基体制备微弧氧化薄膜。利用X射线衍射分析手段对制得的微弧氧化膜层进行相结构分析,通过扫描电子显微镜对氧化膜层的表面、横截面及断口等进行研究,还探讨了表面疏松层和致密层的形成机制。研究结果表明:制得的镁合金微弧氧化膜由MgO, MgSiO₃和MgAl₂O₄等相组成;微弧氧化膜层由表面疏松层和致密层构成;镁合金微弧氧化形成的表面疏松层为多孔结构,这种孔呈网络结构分布;而形成的致密层结构非常致密,没有发现孔洞,而且它和基体的结合非常紧密;表面疏松层和致密层是经过“成膜→击穿→溶化→凝固→烧结……”等一系列循环过程形成的。

Abstract: Micro-arc oxidation (MAO) ceramic coating on AZ91 magnesium alloy was prepared in a silicate alkaline solution. The experiments were carried out in current constant-current mode at the current density of 20 A/dm². The phase structure and compositions were studied by means of X-ray diffraction. The surface, cross section and fracture surface of MAO coating also were observed by means of scanning electron microscope. The results show that the MAO coating mainly consists of MgO, MgSiO₃ and MgAl₂O₄. The MAO coating on magnesium alloy is composed of a porous outer layer and a dense inner layer. The structure of the MAO porous coating is a network structure composed of interconnected needle-like holes. The dense inner layer is very compact and bonded tightly with the magnesium alloy base. The MAO coating is formed by the repeating process of“film forming→breakdown→melting→freezing→sintering…”.