AZ91D镁合金微弧氧化膜微观形貌及形成过程研究

采用扫描电镜和金相显微镜系统研究了系列电压下AZ91D镁合金的表面氧化膜形成过程,讨论了微弧氧化膜层形成规律及成膜机制。结果表明:在试验电压范围内,微弧氧化起弧过程可以分为3个阶段:第1阶段为局部腐蚀与氧化相互竞争阶段,在表面缺陷处首先开始腐蚀,形成疏松的氧化膜,同时伴随水的电解过程;第2阶段为微区放电阶段,表面整体被氧化,形成少量孔洞的较致密氧化膜层,水的电解过程加剧;第3阶段为弧光放电阶段,氧化剧烈,膜层在电弧作用下击穿形成连通的孔洞,且孔洞直径和数量增加。

Microstructure and Formation of Micro-arc Oxidation Coatings of AZ91D Magnesium Alloys

The form of the oxidation coatings on the AZ91D magnesium alloy under different processing conditions was studied by optical microscope and the scanning electron microscope, the forming mechanism of coatings was also discussed. The results showed that under the test voltages, the process before arcing could be divided to three stages: the first stage is the competing stage between partly corrosion and oxidation, the corrosion begins at the defects of the surfaces firstly and loosen oxidation coatings are forming, at the same time electrolysis of water happens; the second stage is the microcell discharging stage, the surfaces are oxidized integrally and compact oxidation coatings with a few pores are formed, the electrolysis of water is aggravated; the third stage is the arcing discharging stage, the oxidation process becomes more drastic, the formed coatings are punctured by arcing to form connected pores, and the size and number of pores are increased.