Pezzato L, Gennari C, Franceschi M, Brunelli K
Department of Industrial Engineering, University of Padua, Via Marzolo 9, 35131, Padova, Italy.
Sci Rep. 2022 Aug 22;12(1):14329. doi: 10.1038/s41598-022-18176-x.
In this work, plasma electrolytic oxidation (PEO) process was applied on AlSi10Mg samples, produced with laser powder bed fusion (L-PBF), in the as printed condition and after different heat treatments, and, for comparison, on as-cast samples of AlSi10Mg. PEO process was performed in direct-current mode using high current densities and short time in a basic silicate electrolyte. For the first time, the effects of silicon morphology in L-PBF AlSi10Mg samples, in as printed condition and after different heat treatments, on the obtained PEO coating were investigated in terms of microstructure and corrosion properties. The microstructure of the substrate was characterized with optical and electron microscopy observations (optical microscopy OM, scanning electron microscopy SEM, and transmission electron microscopy TEM) and with X-ray diffraction (XRD). The analysis showed that heat treatments of annealing and solution treating modified the morphology and distribution of silicon in the samples obtained through L-PBF. The PEO coated samples were characterized with SEM, both on the surface and in the cross-section, and compositional analysis were performed with energy dispersive spectroscopy (EDS) analysis and elemental mapping. The coatings were also analyzed with XRD and the corrosion properties evaluated through electrochemical impedance spectroscopy (EIS) tests. Also microhardness tests were performed on the substrates and on the coatings. The microstructure of the coatings was strongly influenced by the silicon distribution. In particular, a non-uniform distribution of silicon and the presence of iron-rich intermetallic (obtained in the as-cast and solution treated samples) induced the formation of more porous and thinner coatings in comparison with the ones obtained in the as printed and annealed samples. The not-uniform silicon distribution produced a not-homogenous distribution of silicon into the coatings. The particular cellular structure of the as printed sample induced the formation of a coating with a higher amorphous fraction, in comparison with the ones produced on the other samples. The higher thickness and lower porosity of the coatings obtained on the annealed and as printed samples resulted in an increase of the corrosion resistance.
在本研究中，对采用激光粉末床熔融（L-PBF）制备的AlSi10Mg样品在打印态及不同热处理后进行了等离子体电解氧化（PEO）处理，并且为作比较，也对AlSi10Mg铸态样品进行了该处理。PEO处理在碱性硅酸盐电解液中采用直流模式，使用高电流密度并在短时间内进行。首次从微观结构和腐蚀性能方面研究了打印态及不同热处理后的L-PBF AlSi10Mg样品中硅形态对所得PEO涂层的影响。通过光学和电子显微镜观察（光学显微镜OM、扫描电子显微镜SEM和透射电子显微镜TEM）以及X射线衍射（XRD）对基体的微观结构进行了表征。分析表明，退火和固溶处理改变了通过L-PBF获得的样品中硅的形态和分布。对PEO涂层样品进行了表面和横截面的SEM表征，并通过能谱（EDS）分析和元素映射进行了成分分析。还对涂层进行了XRD分析，并通过电化学阻抗谱（EIS）测试评估了腐蚀性能。此外，还对基体和涂层进行了显微硬度测试。涂层的微观结构受硅分布的强烈影响。特别是，与打印态和退火态样品相比，硅的不均匀分布以及富铁金属间化合物的存在（在铸态和固溶处理样品中获得）导致形成了更多孔且更薄的涂层。硅分布不均匀导致硅在涂层中分布不均匀。与在其他样品上制备的涂层相比，打印态样品特有的胞状结构导致形成了具有更高非晶分数的涂层。在退火态和打印态样品上获得的涂层具有更高的厚度和更低的孔隙率，从而提高了耐腐蚀性。
