LA103Z镁锂合金微弧氧化膜层微观组织及腐蚀行为

Microstructure and Corrosion Behavior of Micro-arc Oxidation Ceramic Coatings Prepared on LA103Z Magnesium-Lithium Alloy

以硅酸盐为电解液体系,采用微弧氧化技术(MAO)在LA103Z镁锂合金表面制备陶瓷层,研究了不同电压对陶瓷层微观形貌和耐蚀性的影响。利用SEM、XRD等手段对膜层微观形貌、相组成进行表征,采用析氢法、失重分析法对膜层的耐蚀性进行评估。结果表明,MAO陶瓷层在生长40 s后,表面逐渐形成微孔状形貌。随着氧化电压增大,膜层厚度和表面微孔孔径增大,呈现出"火山口"形貌,膜层表面有裂纹出现。MAO陶瓷层主要由MgO和Mg2SiO4相组成。不同氧化电压所制备的MAO陶瓷层浸泡192 h后的析氢速率大小顺序为:v450 V<v500 V<v550 V<v基体。此外,氧化电压为500 V的MAO陶瓷层浸泡96 h后具有最小的质量损失率,说明MAO陶瓷层可以提高基体耐蚀性,且500 V所制备的MAO陶瓷层保护能力更优。

The micro-arc oxidization(MAO) ceramic layer on LA103 Z Mg-Li alloy was prepared in silicate alkaline electrolyte. The effects of oxidation voltage on microstructure and corrosion behavior of MAO coatings in 3.5% NaCl solution were investigated. The microstructure and phase composition of the coatings were characterized by SEM and XRD. In addition, the corrosion resistance of the ceramic layers was evaluated by hydrogen evolution method and weight loss analysis. The results indicate that the micro-porous morphology of MAO coating is formed gradually after growing for 40 s. Meanwhile, the thickness and micro-pore diameter of the coatings are increased with the enhancement of oxidation voltage, where the "crater" morphologies and the micro-cracks appear on the surface of the ceramic layer. The MAO coating is mainly composed of MgO and Mg2SiO4 phases. The hydrogen evolution rate of MAO coatings prepared with different oxidation voltages after 192 h immersion is presented as follows: v450 V<v500 V<v550 V<vsubstrate. Furthermore, the MAO coating with an oxidation voltage of 500 V has a minimum weight loss rate after immersion for 96 h. It is demonstrated that MAO coating can provide a positive corrosion protection for the substrate and the MAO coating prepared with 500 V has the desirable anticorrosion capacity.