Effects of Nano-TiO2 Particles on Structure and Properties of Micro-arc Oxidation Film on Al-Li Alloy

To improve the corrosion resistance and mechanical properties of micro-arc oxidation film, 2297 Al-Li alloy was treated by micro-arc oxidation after adding TiO2 nanoparticles into electrolyte. The effects of TiO2 nanoparticles on the microstructure, mechanical properties and corrosion resistance of micro-arc oxidation film were studied by means of SEM, XRD, EDS, glow discharge and electrochemical test techniques. Results show that micro-arc oxidation film becomes flat and dense after addition of TiO2 nanoparticles. With the increase of the amount of TiO2 nanoparticles, pore size of discharge channel decreases and the number of discharge channel increases. TiO2 nanoparticles can inhibit the contact of molten Al2O3 with in the electrolyte and therefore, the content of Si element in the film decreases (from initial 10.27 at.% to 3.10 at.%) as increasing TiO2 nanoparticles additive amount. Results of micro- hardness test show that the hardness of the film is improved because the introduction of TiO2 nanoparticles increases the compactness of the film. Micro-hardness increases by 15% after adding TiO2 nanoparticles by 1 g/L. The appropriate addition of TiO2 nanoparticles can improve the corrosion resistance of the film under the same micro-arc oxidation conditions, but the excessive addition will lead to the decrease of the corrosion resistance of the film due to the increase of the number of discharge channels.