ABSTRACT

Micro-arc oxidation (MAO) coatings were fabricated on 2195 aluminium-lithium alloy substrate, using a silicate and phosphate electrolyte with variable scandium nitrate (Sc(NO₃)₃) concentrations. The properties of the coatings were analysed by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical workstation. The comprehensive analysis demonstrates that adding proper amount of Sc(NO₃)₃ increased the oxidation voltage, which transformed the worm shape discharge micropores into round-hole shape, and the MAO coatings presented a double-layer structure. The primary phase composition of the coatings was γ-Al₂O₃, α-Al₂O₃, Sc₂O₃ and Al₃Sc. The optimum concentration of Sc(NO₃)₃ was 0.6 g L⁻¹. The hardness reached a maximum value of (1284 ± 43.5) HV, which was about 2.5 times higher than that without adding. The self-corrosion current density reduced from 138.00 × 10⁻⁷ A cm⁻² (substrate) to 3.65 × 10⁻⁷ A cm⁻², which was approximately two orders of magnitude lower, indicating that the corrosion resistance was improved.

摘要

_{使用具有不同硝酸钪 (Sc(NO 3} ) ₃ ) 浓度的硅酸盐和磷酸盐电解液在 2195 铝锂合金基材上制备微弧氧化 (MAO) 涂层。采用扫描电子显微镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)和电化学工作站对涂层的性能进行了分析。综合分析表明，添加适量的Sc(NO ₃ ) ₃提高了氧化电压，使蠕虫状放电微孔变为圆孔状，MAO涂层呈现双层结构。涂层的主相组成为γ-Al ₂ O ₃、α-Al₂ O ₃、Sc ₂ O ₃和Al ₃ Sc。_{Sc(NO 3} ) ₃的最佳浓度为0.6 g L ^-1。硬度达到最大值为（1284±43.5）HV，比不添加时提高约2.5倍。自腐蚀电流密度从138.00 × 10 ^{- 7}  A cm ^-2（基材）降低至3.65 × 10 ^{- 7}  A cm ^-2，大约降低了两个数量级，表明耐腐蚀性能得到提高。