【摘要】 为了探索镁合金微弧氧化表面层多孔结构的形成机制,首先在硅酸盐碱性电解液:5～30g/LNa2SiO3,1～5g/LNaOH,5～8g/LKF,0.5～2.0g/LNa3C6H5O7,0.5～2.0g/LEDTA中,以AZ91镁合金为基体制备出微弧氧化陶瓷膜,采用恒电流控制模式,电流密度为20～50A/dm2。然后通过透射电镜(TEM)和扫描电镜(SEM)观察膜层的表面和横断面结构。结果发现,表面微孔有两种形态,一种呈蜂窝状结构,另一种呈豆瓣状突起结构;同时还观察到了这种孔的形成和衍化过程,其中包括微孔的形成、生长、联接、合并和嵌套等过程。从而得到如下结论:镁合金表面多孔层的形成是一种层进生长模式;镁合金微弧氧化中微孔的萌生是按"气体喷射"机制进行,而孔的发展是按"蜂巢衍进"模式进行。更多还原

【Abstract】 Micro-arc oxidation ceramic(MAO)coating was prepared on AZ91 magnesium alloy from a silicate alkaline solution composed of 5.0～ 30.0g/L Na2 SiO3,1.0-5.0 g/L NaOH,5.0-8.0 g/L KF,0.5～2.0 g/L Na3C6H5Q7,and 0.5～2.0 g/L ethylene diamine tetraacetic acid(EDTA),in alternating current galvanostatic mode and at a cur-rent density of 20-50 A/dm2.The surface and cross-section morphologies of the MAO coating were observed using a transmis-sion electron microscope(TEM)and scanning electron micro-scope(SEM),and the mechanisms for the formation of porous microstructures of the MAO coating were discussed.Results indi-cated that two types of pores,i.e.,honeycomb-like and bean-shaped pores were formed in the MAO coating.The formation and growth processes of the MAO coating included initiating,grow-ing,connecting,merging,and nesting processes of the pores.The formation of the porous coating on the surface of Mg alloys was dominated by layer-by-layer growth,while the pore initiation was dominated by gas ejecting mechanism and the pore develop-ment by cellular evolution mechanism.更多还原