| Pure magnesium and its alloy, with elastic modulius (about 40 GPa) much closer to that of the natural bone, can enable to avoid the"stress shield"effect when implanted into human bodies as bone replacement materials. However, the low corrosion resistance of magnesium and its alloy, especially in body solutions containing Cl-, has restricted its extensive application as bone implant materials. So, the surface protective methods are necessary to provide the control of corrosion rate. In this thesis, the pure titanium layers were prepared by cold spraying and magnetism sputtering, respectively. Then, microarc oxidation (MAO) method was used to fabricate bioactivity outer layer on the titanium layer surface. For contrast, microarc oxidation layers were also prepared on AZ91D. Microstructure and phase composition of the layers were characterized by SEM,XRD and EDS. The corrosion resistance properties in simulate body fluid (SBF) were evaluated by AC impedance.The results showed that the cold spraying titanium layers (CS) are rough on the surface, with a thickness of 100μm. After the microarc oxidation treatment, the newly formed layers on the bottom CS layers surface are porous, mainly composed of Ti6O, and a small amount of products containing Ca and P are also observed. The newly formed MAO layers are beneficial to improve the density and bioactivity. The magnetism sputtering titanium layers (MS) are compact and smooth on the surface, with a thickness less than 5μm. After being subjected to the microarc oxidation treatment, the newly formed top layers on the MS layers are rough, and the granular products are mainly composed of Ti6O. The MAO layers formed on AZ91D in two electrolytes with F- and PO43-, respectively, are mainly composed of MgO and Al2O3, meanwhile, with the rising voltage, thickness and surface porosity of the layers increase. However, the harmful component F was found in the layer formed in the electrolyte containing F-, and bioactivity component P was found in PO43- electrolyte.Results of AC impedance test on AZ91D and composite layers showed that the Nyquist curve of AZ91D is characterized by a captance arc in high frequency and a positive reactance arc in low frequency. With increasing of soaking time, the charge resistance falls down from 560 to 170Ω/cm2. The Nyquist curve of MAO layer on AZ91D consists of captance arc in high frequency and low frequency, respectively. With increasing of soaking time, the charge resistance falls down from 9300 to 60Ω/cm2. The Nyquist curve of MS layers is featured by a captance arc in high frequency and a positive reactance arc in low frequency, and the charge resistance is 41Ω/cm2, which indicates that no passivation takes place in SBF. After MAO treatment of MS layers, the Nyquist curve only contains a captance arc. And, with the soaking period prolonged, the charge resistance falls down from 60 to 40Ω/cm2. Comparing with the scale of charge resistance falling down, the corrosion resistance of composite layers shows better than those of AZ91D and its MAO layers.
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