微弧氧化对车用AZ31B镁合金磷酸盐转化膜组织和耐腐蚀性能的影响

Effects of Micro-Arc Oxidation on Microstructure and Corrosion Resistance Properties of Phosphate Conversion Film on AZ31B Magnesium Alloy for Automotive Use

为了提高车用AZ31B镁合金磷酸盐转化膜的耐腐蚀性能,采用微弧氧化的方法对其表面进行加强,并测试研究了微弧氧化前后磷酸盐转化膜的组织和耐腐蚀性能。结果表明:磷酸盐转化膜经过微弧氧化增强处理后得到了尺寸更小的微孔,提高了整体膜的致密度并获得更平整表面。微弧氧化后膜内形成了新的MoSi2相,对膜表面微孔形成填充状态,使孔隙率明显减小。在磷酸盐转化膜表面进行微弧氧化处理会对其实现有效的增强。经过微弧氧化处理后粗糙度明显降低。对磷酸盐转化膜进行微弧氧化后再进行浸泡处理没有出现膜腐蚀情况,对基体也实现了良好覆盖状态。随浸泡时间延长,膜腐蚀速率表现出先增高后降低又增高的变化规律。

In order to improve the corrosion resistance of AZ31B magnesium alloy phosphate conversion film for automotive use,the surface was strengthened by the micro-arc oxidation. The microstructure and corrosion resistance properties of phosphate conversion films before and after micro-arc oxidation were studied. Results showed that the phosphate conversion film was treated with micro-arc oxidation enhancement to obtain smaller micropores,higher densification and smoother surface. After micro-arc oxidation,a new MoSi2 phase was formed in the film,which filled the micropores on the film surface and significantly reduced the porosity. The micro-arc oxidation treatment on the surface of phosphate conversion film effectively enhanced the surface. After micro-arc oxidation,the roughness was also decreased obviously. After the soaking treatment,the phosphate conversion film by micro-arc oxidation did not corrode and the matrix was covered well. When the soaking time increased,the corrosion rate of the film increased first,then decreased and then increased again.