AZ31镁合金微弧氧化腐蚀行为及耐蚀性的研究

发布时间：2018-05-12 04:35

本文选题：微弧氧化 + 盐雾试验　；参考：《燕山大学》2015年硕士论文

【摘要】：镁合金由于具有优良的机械性能,已开始被大量运用在航空、汽车等行业,但其较差的耐蚀性制约着镁合金的进一步发展。本文通过运用自制的WH-1A型微弧氧化系统控制柜对AZ31镁合金进行微弧氧化处理,利用电化学方法研究了微弧氧化试样在盐雾试验测试环境下的腐蚀过程,系统的研究了硅酸钠添加剂对微弧氧化试样耐蚀性的影响,对比了不同的电解液添加剂对微弧氧化试样耐蚀性的影响。研究表明AZ31镁合金微弧氧化试样表面分布着放电孔洞及裂纹,当盐雾试验测试时间达到24h时,试样表面放电孔洞及裂纹分布着许多腐蚀产物,物相分析结果表明腐蚀产物为Mg(OH)2,电化学测试结果表明试样陶瓷层外层耐蚀性相对增强,内层耐蚀性降低,试样的半导体特性由N型变为P型。盐雾试验测试时间达到72h时,试样表面放电孔洞及裂纹被腐蚀产物所覆盖,试样耐蚀性进一步增强。当盐雾腐蚀时间达到120h时,试样表面产生微裂纹,耐蚀性变差。随着微弧氧化时间的延长,电解液添加硅酸钠的微弧氧化试样表面粗糙度增加,试样所含MgO物相的相对摩尔百分含量增加,物相Mg2SiO4和MgSiO3相对摩尔百分含量降低。电化学数据表明AZ31镁合金基体耐蚀性最差,所制得的试样中微弧氧化时间30s的试样耐蚀性相对最好,随着微弧氧化时间的延长,试样耐蚀性变差。微弧氧化时间分别为1min、5min、15min的试样经过0.1mol/L的Na2SiO3溶液浸泡40min后,电化学数据表明三种试样耐蚀性相差不大,说明不同时间下得到的微弧氧化试样对耐蚀性起主要作用的是陶瓷层内层。电解液中含有不同添加剂所形成的微弧氧化试样表面形貌差异明显,试样含有的物相也不相同。微弧氧化电解液添加硅酸盐有利于陶瓷层的快速生长,电解液添加偏铝酸盐制得的陶瓷层表现出典型的内外双层结构,电解液添加磷酸盐所制得的陶瓷层的致密性较好,电解液添加氟化物所制得陶瓷层致密性最好。
[Abstract]:Magnesium alloys have been widely used in aviation, automobile and other industries because of their excellent mechanical properties, but their poor corrosion resistance restricts the further development of magnesium alloys. In this paper, the micro-arc oxidation treatment of AZ31 magnesium alloy was carried out by using self-made WH-1A micro-arc oxidation system control cabinet. The corrosion process of micro-arc oxidation samples under salt spray test environment was studied by electrochemical method. The effect of sodium silicate additive on corrosion resistance of micro-arc oxidation samples was systematically studied, and the effects of different electrolyte additives on corrosion resistance of micro-arc oxidation samples were compared. The results show that there are discharge holes and cracks on the surface of AZ31 magnesium alloy micro-arc oxidation samples. When the test time of salt spray test reaches 24 hours, many corrosion products are distributed in the discharge holes and cracks on the surface of AZ31 magnesium alloy. The results of phase analysis show that the corrosion product is MgOH ~ (2 +). The electrochemical test results show that the corrosion resistance of the ceramic layer is relatively enhanced, the corrosion resistance of the inner layer is decreased, and the semiconductor property of the sample is changed from N-type to P-type. When the test time of salt spray test reached 72 hours, the surface discharge holes and cracks were covered by corrosion products, and the corrosion resistance of the samples was further enhanced. When the corrosion time of salt spray is up to 120 h, the micro-cracks on the surface of the sample are produced, and the corrosion resistance becomes worse. With the prolongation of the time of microarc oxidation, the surface roughness of the samples added with sodium silicate increases, the relative molar percent content of MgO phase increases, and the relative molar percent content of Mg2SiO4 and MgSiO3 decreases. Electrochemical data show that the corrosion resistance of AZ31 magnesium alloy matrix is the worst. The corrosion resistance of the samples prepared by micro-arc oxidation for 30s is the best, and the corrosion resistance of the samples becomes worse with the prolongation of the micro-arc oxidation time. After the samples with microarc oxidation time of 1 min or 5 min or 15 min were soaked in Na2SiO3 solution of 0.1mol/L, the electrochemical data showed that the corrosion resistance of the three samples had little difference, which indicated that the ceramic layer inner layer played a major role in the corrosion resistance of the samples obtained at different time. The surface morphology of the samples formed by micro-arc oxidation with different additives in the electrolyte is different, and the phase of the samples is also different. The addition of silicate into the electrolyte of micro-arc oxidation is beneficial to the rapid growth of the ceramic layer. The ceramic layer prepared by adding metaluminate to the electrolyte shows a typical internal and external double layer structure, and the ceramic layer made by adding phosphate into the electrolyte has a good compactness. The ceramic layer prepared by adding fluoride into electrolyte has the best compactness.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG174.4

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