Study On Microstructure And Properties Of Al-Al 2 O 3 Composite Film And Multilayer Film

The nano composite structures and nano multilayer structures not only have the characteristics of super hard,but also can improve the toughness,wear resistance and corrosion resistance of materials.They are the ideal material structures with excellent comprehensive properties in wear resistance and corrosion resistance fields.Because of its high hardness,wear resistance,corrosion resistance,high temperature stability and other excellent properties,Al₂O₃ films deposited by RF magnetron sputtering are deeply concerned.However,the practical experience shows that Al₂O₃ belongs to the brittleness material and is prone to brittle delamination failure.Its application is limited in the mechanical field.Owing to its good ductility and good adhesion,Al thin films can withstand greater tensile or impact deformation.Al films prepared by vacuum evaporation and sputtering deposition have holes,microcracks and other defects.So the application of Al films is limited in corrosion protection field.It is thus obvious that there is a performance complementarity between Al films and Al₂O₃ films.Therefore,the Al-Al₂O₃ composite films and multilayer films prepeared by the method of the combination of DC and RF magnetron sputtering in this paper.The composition,structures,properties of the films were characterized and tested by X ray photoelectron spectroscopy,X ray diffraction,high resolution transmission electron microscopy,field emission scanning electron microscopy,indentation tester,material surface properties tester and electrochemical workstation and micro force testing machine.By adjusting the Al target power,the Al-Al₂O₃ composite films with different Al content were prepared under the condition of the constant Al₂O₃ target power.The composition,structures and morphologies of the composite films were characterized.The effects of Al content on adhesion,hardness and wear resistance of the films were discussed.The results of the study show that the composite films with different Al content show strong Al（111）preferred orientation,and the Al₂O₃ phase exist in amorphous form.The Al-Al₂O₃ composite films are the crystal-amorphous composite structures.The addition of aluminum refines amorphous alumina particles in the composite films.The surface roughness of the Al-Al₂O₃ composite films decrease obviously.But with the increase of Al content（increase of Al target power）,the Al grain size and the surface roughness of the composite films increase.Owing to the combined effect of soft phase Al and small size effect,the hardness and adhesion of the A-A₂O₃ composite films with different Al content are higher than that of pure A₂O₃ film and the wear resistance performance is improved obviously.The adhesion of the Al-Al₂O₃ composite film with the content of Al is 47.8 at.%is the best.The comprehensive properties of the Al-Al₂O₃ composite film with the content of Al is 35.3 at.%is the most excellent.The hardness and average friction coefficient of the Al-Al₂O₃ composite film are 14.4 GPa,0.15 respectively.By adjusting the Al₂O₃ target power,the Al-Al₂O₃ composite films with different Al₂O₃ content were prepared under the condition of the constant Al target power.The composition,structures and morphologies of the composite films were characterized.The effects of Al₂O₃ content on adhesion and corrosion resistance of the films were discussed.The results of the study show the Al-Al₂O₃ composite films are the crystal-amorphous composite structures.The amorphous Al₂O₃ interrupt the columnar growth of Al phase and fill the micro defects in Al phase.The Al-Al₂O₃ composite films have excellent corrosion resistance.The corrosion current density Icorr of the composite film with the content of Al₂O₃ is 56.8 at.%is 0.0016 mA/cm2.The value is an order of magnitude lower than that of the pure Al film.The Al/Al₂O₃ multilayer films with different modulation ratio were prepared by double targets alternate deposition.The microstructures and morphologies of the multilayer films were characterized.The tensile properties and corrosion resistance of the films were discussed.The results of the study show that the Al layers of the Al/Al₂O₃ multilayer films have preferred orientation of Al（111）and the Al₂O₃ layers are amorphous.The multilayer films show the good modulation structures.The modulation ratio is smaller,the surface of the multilayer films is more dense and the interfaces of the multilayer films are flatter.The yield strength of the Al/Al₂O₃ multilayer films decrease with the increasing modulation ratio.The thickness of layer Al and the multilayer interfaces between layers are the factors influencing the yield strength of multilayer films.The ductility of the multilayer films increase with the increasing modulation ratio monotonously.This is largely the result of inhibitory effect of plastic deformation of Al layer on the micro cracks and the action of interlayer interfaces of multilayer films.The corrosion resistance of the Al/Al₂O₃ multilayer films decrease with the inceasing modulation ratio.It mainly depends on corrosion inhibition of the surface and interfaces of the Al/Al₂O₃ multilayers.