四硼酸钠浓度对6061铝合金微弧氧化涂层结构及性能的影响

Effect of Concentration of Na_2B_4O_7·10H_2O on Structure and Performance of Micro-Arc Oxidation Coatings Formed on 6061 Aluminum Alloy

采用以四硼酸钠(Na_2B_4O_7·10H_2O)为主的电解液对铝合金微弧氧化可提高膜层的硬度等,但未见系统研究四硼酸钠浓度对微弧氧化膜层结构和性能影响的报道。采用恒电压模式在四硼酸钠碱性溶液中对6061铝合金进行微弧氧化,通过扫描电镜(SEM)、X射线衍射仪(XRD)对氧化陶瓷层的组织结构进行分析,并考察了四硼酸钠浓度对氧化涂层显微组织、硬度、耐磨和耐蚀性能的影响。结果表明:制备的氧化层由疏松层和致密层组成,其中致密层占总膜厚度的75%以上,且与基体材料形成冶金结合;氧化膜层中出现了γ-Al_2O_3和α-Al_2O_3两相,其中γ-Al_2O_3相较多,γ-Al_2O_3和α-Al_2O_3两相的晶化程度不随着电解液里四硼酸钠浓度的变化而变化;氧化膜层具有高的显微硬度和低的表面粗糙度,二者不随电解液四硼酸钠浓度的变化而变化;微弧氧化后6061铝合金耐磨性和耐蚀性提高。

6061 aluminum alloy was surface- treated by micro-arc oxidation(MAO) under constant voltage mode in an alkaline aqueous solution with sodium borate,and the structure and composition of prepared MAO ceramic coatings were studied by scanning electron microscope and X-ray diffractometer(XRD),and the effect of sodium borate concentration on microstructure and properties of the ceramic coatings was further investigated.Results showed that the prepared oxidation coating was consisted of loose layer and dense layer.The thickness of dense layer accounted for more than 75%among the thickness of total layer,and the dense layer metallurgical combined to the substrate.Both γ-Al_2O_3 phase and α-Al_2O_3 phase were observed in the ceramic coatings,and the amount of γ-Al_2O_3 phase was more than that of α-Al_2O_3phase,which was no relevant to the change of sodium borate concentration in electrolyte.Besides,the MAO coating possessed high hardness and low thickness,both of which did not change as the concentration of sodium borate in electrolyte.After treated by micro- arc oxidation,the abrasive resistance and corrosion resistance of 6061 Al alloy were improved.