To solve the problems generally encountered during the plasma electrolytic oxidation(PEO) of Al alloys with high Si content, a pretreatment of chemical etching was applied before the process. The influence of such pretreatment was studied by SEM, EDS and XRD. The pretreatment presents a significant effect on positive voltage at the beginning stage of PEO, leading to higher voltage over the whole process. The difference between the positive voltages of non-etched and etched specimens decreases gradually with the increase of processing time. The pretreatment exhibits much less influence on the negative voltage. For the sample with surface pretreatment, the average growth rate of PEO coating is increased from 0.50 to 0.84 μm·min-1and the energy consumption is decreased from 6.30 to 4.36 k W·h·μm-1·m-2. At the same time, both mullite and amorphous Si O2 contents are decreased in the coating.
Ba(OH)2电解液中,分别采用交/直流源微弧氧化法在Ti基体表面制备了钛酸钡薄膜,并分别研究了两种薄膜的生长方式及微观结构。结果表明:交、直流源模式下所得Ba Ti O3薄膜的晶体结构分别主要由六方相、四方相构成;交流模式下薄膜从试样边角向中心呈层片状生长,直流模式下薄膜生长则主要依靠缓慢移动的连续电弧在膜层较薄弱区域发生的放电击穿;交流源模式下所得薄膜表面较平整、致密性较好;两种电流源模式下所得膜层均分布着大小不一的微弧氧化孔洞,但直流源模式下所得薄膜中孔洞分布较少。
