AZ31B镁合金表面合金化涂层的显微组织和耐腐蚀性能

摘要

Vacuum thermal diffusion technique was applied to preparing alloying coating on AZ31B magnesium alloy. The microstructure and phase composition of the coatings prepared at different holding time were investigated in detail using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD), and so on. The microhardness tester and electrochemical workstation (PS−168a) were used to measure the microhardness and corrosion resistance of the alloying coating. The results showed that the alloying coatings gradually generated with the extension of holding time under constant temperature. And the obvious bonding interface between the coating and substrate was observed, and the bonding interface was changed from smooth to zigzag. EDS and XRD analyses showed that the microstructure of alloying coating mainly consisted of eutectic α-Mg phase and continuous network β-Al12Mg17 phase. The average microhardness of the coatings increased by 113%in comparison to the substrate, and the self-corrosion potential increased from−1.389 to−1.268 V at the same time.%通过真空热扩渗技术在AZ31B镁合金表面制备一层合金化涂层。采用OM、SEM、EDS及XRD等方法分析合金化涂层的显微组织、成分和相组成，并利用显微硬度计和PS−168a型电化学腐蚀测试系统分别对合金化涂层的显微硬度和耐腐蚀性能进行测试分析。研究结果表明：恒温条件下，随着保温时间的延长，在 AZ31B 镁合金表面可以形成合金化涂层。随着保温时间的延长，涂层与基体之间结合界面形貌由平直结合转变成“锯齿”状咬合；且合金化涂层与基体之间存在明显的过渡层，过渡层逐渐变宽。EDS及XRD分析结果表明，合金化涂层为Mg−Al共晶组织α-Mg和β-Al12Mg17，合金化涂层的平均显微硬度比基体的平均显微硬度提高了113%；自腐蚀电位也由基体的−1.389 V提高到−1.268 V。