5083铝合金表面单致密微弧氧化膜的制备及其性能研究

Preparation and Properties of Micro-arc Oxide Film with Single Dense Layer on Surface of 5083 Aluminum Alloy

采用响应曲面法对微弧氧化电解液体系进行了优化,并在5083铝合金表面进行了单致密微弧氧化涂层的制备。通过扫描电镜、X射线衍射仪、显微硬度计和极化曲线对铝合金微弧氧化膜的微观组织、显微硬度和耐蚀性进行了研究。结果表明:随着微弧氧化膜层厚度从30μm增加到90μm,烧结颗粒的尺寸从约为10μm增加到约为50μm,致密层由最初的20μm增加到70μm,陶瓷膜层中α-Al2O3的比例明显增加,涂层的硬度由900 HV提高到1500 HV。依据极化曲线和盐雾实验结果发现:随着微弧氧化时间的增加,微弧氧化膜的自腐蚀电流密度逐渐降低,钝化能力逐渐增强,膜层的耐腐蚀性能大幅度提高。

Marine Al-alloy 5083 owns low density,good weldability and high hardness,but it is easily suffered from pitting corrosion in sea water due to the effect of Cl-.Micro-arc oxidation(MAO)is an effective way to improve the corrosion resistance of Al-alloy.In the present study the electrolyte formula was optimized via response surface methodology so that to acquire a novel MAO coating on Al-alloy 5083,which composed of merely a dense layer.The prepare MAO coating was then characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),micro-hardness meter and dynamic polarization technology in terms of microstructure,micro-hardness and corrosion resistance.Results showed that in comparison with the coating prepared with the ordinary electrolyte,the thickness of the MAO coating increases from 30μm to 90μm,size of the sintered particles on MAO coating grown from 10μm to 50μm,and the thickness of the dense layer increased from 20μm to 70μm,accompanied by the increase of the percentage ofα-Al2O3 in the MAO coating as well.The hardness of the polished MAO coating increased from 900 HV to 1500 HV.Polarization curve and salt frog test results also found that with the increasing of micro-arc oxidation time,the corrosion current density of MAO coating was gradually decreased,while its passivation ability was enhanced.Therefore,corrosion resistance of Al-alloy 5083 was increased substantially in the presence of the MAO coating composed merely of a thick dense layer.