Research On The Effect Of Mechanical Grinding On TA2 And Its Anodic Oxide Film

Surface mechanical attrition treatment?SMAT?can form a layer of nanocrystalline on metal surface,the surface properties of objects with nanocrystalline layers have changed greatly compared with the original bulk materials.However,in the process of SMAT,a great compressive stress is produced on the surface of material,and the thermodynamic properties changed.Therefore,it is also worthy to focus on the influence of compressive stress and surface thermodynamics on the properties of nanocrystalline.The titanium surface oxide film produced by anodic oxidation has been widely used in many fields,such as corrosion protection,decorating materials,new energy materials and hydrogen production,which thanks to its advantages of corrosion resistance,decorative property,photocatalysis,and the preparation process is also simple,low cost and less pollution.There are many factors affecting anodic oxidation,but there is little research on the influence of matrix material on anodic oxidation.In this paper,the industrial pure titanium?TA2?was used as the matrix material,the effect of SMAT on matrix material and anodic oxidation process was effected by different conditions of matrix materials was studied.Titanium anodic oxide film was prepared in 0.5M H₂SO₄ electrolyte,the matrix and oxide film was characterized by SEM,XPS,Raman test,electrochemical test and UV-Vis DRS.The influence of SMAT on the residual stress and surface thermodynamics of TA2 substrate and the effect of SMAT on the properties of anodized film were studied.According to the conclusion,the surface mechanical attrition treatment can bring on severe plastic deformation on the surface.When the treatment time increased to 45min,cracks appeared on the surface of TA2,the mechanical treatment of TA2 is expected to achieve the purpose of refining the surface grain,increasing residual stress and improving the surface activity;the surface residual stress of samples were increased by SMAT,being 5.2-7 times that of the without treatment sample.The increased of residual stress caused the increase of standard molar entropy and Gibbs free energy of standard molar formation on the surface of TA2,it provides a good growth condition for anodic oxidation.The TA2 substrate after SMAT has a significant effect on the formation of oxide film,the high surface of the substrate increased the thickness and color depth of the oxide film.The oxygen content in oxide film was increased,SMAT promoted the transformation of metastable Ti²⁺,Ti³⁺to steady-state Ti⁴⁺.And the passive films consisted maunly of TiO₂ and TiO₂·H₂O.The increase of the surface energy reduces the Gibbs generation free energy of the Ti compound.The increase of the growth rate of oxide film reduces the defects in the oxide film,the carrier bulk density of the samples treated by 30min mechanical grinding is reduced by one order of magnitude compared with that of TA2 samples;Inner oxide film is denser,the self-corrosion potential was increased from-1.36V to-1.0^-1.15V,and the self-corrosion current density was decreased from 1.15×10^-4A·cm^-1 to 4.17-9.0×10^-5A·cm^-2,being 26.5%increase and 63.7%decrease in largest respectively,the corrosion resistance increased significantly;After heat treatment,the content of TiO₂ in the oxidized film is improved and the absorption resistance of visible light is increased.After mechanical grinding,the surface energy of the oxide film decreases,which results in the increase of the wetting angle and the hydrophobicity of the oxide film.