含石墨微粒的电解液中电流密度对ZL108微弧氧化膜层特性的影响

Effects of current densities on ZL108 Aluminum alloy MAO coatings in an electrolyte containing graphite micro-particles

摘要:

在含石墨微粒的硅酸钠电解液中，采用不同的电流密度（1, 5, 10，15和20 A/dm2）在ZL108铝合金上制备了微弧氧化（MAO）膜层。利用SEM、EDS、XRD、涡流测厚仪和显微硬度计对微弧氧化膜层的特性进行了研究。结果表明，随着电流密度的增加，微弧氧化膜层的增厚导致氧化电压增加。微弧氧化膜表面多孔，微孔的直径和烧结盘尺寸逐渐增加。膜层表面C、Si元素的相对含量随电流密度增加而增多，C元素在膜层表面呈均匀分布，膜层截面C元素主要集中在膜层外侧。膜层主要由SiC, SiO2, θ-Al2O3, α-Al2O3组成, SiC相来源于石墨与SiO2反应。随电流密度增大，膜层硬度增加。膜层耐蚀性呈先升高后降低的趋势，并在5A/dm2时膜层腐蚀速率最低。

Abstract:

Micro-arc oxidation (MAO) coatings were prepared on ZL108 aluminum alloy in the Na2SiO3 electrolyte adding graphite micro-particles at different current densities (1, 5, 10, 15 and 20 A/dm2). The characteristics of MAO coatings were studied by SEM, EDS, XRD, eddy-current thickness meter and micro-hardness tester. The result showed that the thickening of MAO coatings led to the increase of the oxidation voltages with the increase of current density. The surface of MAO coatings was porous. The diameter of micro-pore and the size of sintering discs gradually increased. The relative counts of C and Si element on the surface of MAO coatings increased with the increasing of current density. The C element was uniform distribution on the surface of MAO coatings. The C element on cross-sectional of MAO coatings mainly concentrated on outer side. MAO coatings mainly consist of SiC, SiO2, θ-Al2O3, α-Al2O3. The SiC phase derived from the reactions of SiO2 with graphite. With the increase of current density, the MAO coatings hardness increased. MAO coatings prepared at 5A/dm2 exhibited the lowest corrosion rate.