Preparation Of Al-Ce Binary Amorphous Alloy By Magnetron Sputtering And Study On Its Corrosion Resistance

As a high-strength hard aluminum alloy,2024 aluminum alloy is widely used in aircraft skeleton parts such as skins and wings.However,its resistance to local corrosion is poor,which seriously affects the service life of the alloy.Al-Ni-Ce amorphous alloy is used as a new type of high corrosion resistant coating material for surface corrosion protection of 2024 aluminum alloy.At present,the mechanism of elemental action on the corrosion resistance of multi-element amorphous alloys is not comprehensive,mainly due to the complex influence of the precipitated phase in amorphous alloys,and the synergistic effects of various elements in multi-component systems.This topic selects the Al-Ce binary alloy system,eliminates the interference of crystal phase and other elements,and deeply understands the influence of rare earth element cerium on the corrosion resistance of amorphous aluminum alloy,thus guiding the design of Al-Ni-Ce corrosion resistant amorphous alloy coating materials,provides a scientific basis for the application of aluminum-based amorphous alloys as corrosion protection coatings.In this thesis,magnetron sputtering technology is used to prepare Al-Ce binary amorphous alloy.Through the adjustment of sputtering process parameters,alloy thin films with different compositions can be deposited,and X-ray diffraction is used to judge whether the alloy is completely amorphous.Further determining the range of components of the Ce content of the alloy when it can form completely amorphous.The fully amorphous Al-Ce alloy film was tested by electrochemical to study the pitting corrosion resistance of amorphous alloy,and the stability of amorphous alloy passivation film was evaluated by electrochemical impedance spectroscopy,potentiostatic polarization and Mott-Schottky curves.The passivation films of Al-Ce amorphous alloys which formed in different states were analyzed by XPS technology.The effect of the composition and structure of the passivation film on its stability was studied,and the breaking mechanism of the passivation film was proposed.The main conclusions are as follows:(1)The Al-Ce binary alloy film was prepared by magnetron sputtering.The sputtering content increased from 5 W to 20 W,and the Ce content in the deposited alloy film increased from 3.9 at.%to 21.5 at.%.The tendency of the alloy is also gradually increasing.The composition of the Ce content when forming a completely amorphous alloy film ranges from 6.5 to 21.5 at.%;(2)The four amorphous alloys Al93.5Ce6.5,A189Ce11,Al83Ce17 and Al78.5Ce21.5 were electrochemically tested in a 0.01 mol/L NaCl neutral solution.The open circuit potential-time curve indicates that adding the Ce element in A1 can reduce its OCP,and the open circuit potential becomes more negative as the Ce content increases.The potentiodynamic polarization curves show that the difference in passivation current density is not obvious with the increase of Ce content in amorphous alloys,but the pitting potential increases first and then decreases.The alloy Al89Ce11 has the highest pitting potential,which is about-0.07.VSCE;the self-corrosion potential of the alloy gradually decreases,which is consistent with the trend of open circuit potential;the alloy Al89Ce11 has the lowest self-corrosion current density,about 24.25 nA,which is 2-6 times lower than other alloys and has the lowest corrosion rate;(3)Electrochemical impedance spectroscopy shows that Al89Ce11 has the highest total impedance,indicate that the charge transfer resistance is the largest,the resistance in the passivation film is the largest,and the stability is the best..The Mott-Schottky curves of the four amorphous alloys in the passivation interval are positive slopes,indicating that the semiconductor properties of the passivation film of the alloy belong to the n-type semiconductor,and the carrier concentration of Al89Ce11 alloy passivation film is the smallest,and the electron conduction resistance of the passivation film is the largest,indicating the passivation film has the best protection,so it has better corrosion resistance;(4)XPS analysis results of amorphous alloys with different Ce contents indicate that the thickness of the passivation film of Al89Ce11 alloy formed in air and anodic polarization in neutral chloride ion solution is thicker than Al78.5Ce21.5 alloy.When the Ce content is increased to 21.5 at.%,the Al78.5Ce21.5 passivation film contains a large amount of Ce ions,which reduces the stability of the passivation film,so that the Cl ions in the chloride ion-containing solution are not only a large amount on the surface.Adsorption,and can invade into the interior of the passivation film and the passivation film/substrate interface,promoting the breakage of the passivation film,making the alloy more susceptible to pitting.