电流密度对Al-Si合金微弧氧化膜结构及耐蚀性的影响

Influence of current density on microstructure and corrosion resistance of micro-arc oxidation films on Al-Si alloy

采用微弧氧化技术在Al-Si合金表面制备氧化物陶瓷膜层,利用激光共聚焦显微镜、SEM、EDS、XRD、极化曲线等测试方法研究电流密度对Al-Si合金微弧氧化膜层的生长过程、微观结构、元素成分、相组成和耐蚀性的影响规律。结果表明:随电流密度的增大,起弧所需时间减短,膜层厚度和粗糙度均增加,膜层生长速率先增大后减小。电流密度较小时,氧化膜生成相为γ-Al_2O_3,当电流密度达到13.3 A/dm^2时,氧化物生成相出现α-Al_2O_3和莫来石相。当电流密度小于16.6 A/dm^2时,氧化膜的耐蚀性随电流密度增大而增强;当电流密度大于16.6 A/dm^2时,氧化膜耐蚀性能降低,相对于合金基体,氧化膜始钝电位降低,维钝电流密度降低两个数量级。

Micro - arc oxidation （MAO） was used to prepare the coatings on the surface of A1 - Si alloy. The laser scanning confocal microscope （LSCM）, scanning electron microscope （SEM）, energy dispersive spectrometer （EDS）, X-ray diffraction （XRD） and electrochemical polarization curve were utilized to study the influence of current density on the growth process, the microstructure characteristics, the components distribution, and the phase compositions, the corrosion resistance of the micro- arc oxidation coatings on AI-Si alloys. The results show that with the increase of current density, the arc time shortens, the film thickness and surface roughness increase, the film growth rate increases first and then decreases. When the current density is low, the MAO film is mainly consisted of γ-Al2O3. When the current density increases to 13.3 A/dm：, the MAO film is mainly consisted of γ-Al2O3,α-Al2O3 and mullite phase. When the current density is less than 16.6 A/dm：, the corrosion resistances of the MAO films improve with the current density increasing. When the current density is larger than 16.6 A/dm2, the corrosion resistance of MAO film decreases with the current density increasing. Compared with matrix alloy, the passivation current density of the MAO film reduces by two orders of magnitude.