Research On The Influence Of The Corrosion Behavior Of Amorphous Alloys

Due to its unique structure,metallic glasses have excellent mechanical properties and corrosion resistance compared to crystalline alloys.There are a lot of studies on the influencing factors of the mechanical properties and corrosion behavior of metallic glasses,but the corrosion mechanism of metallic glasses is still not clear.In this thesis,three kinds of metallic glasses were selected to systematically study the influence of amorphous structure and composition on its corrosion resistance.The bulk metallic glass((Zr60Cu20Ni8Al7Hf3Ti2 bulk amorphous alloy),binary metallic glass thin film(Zr-Cu metallic glass thin film),and ternary metallic glass thin film(Pd-Ni-P metallic glass thin film)used in this study were prepared by copper mold suction casting method magnetron sputtering method and electroless plating method,respectively.The structure and composition of the metallic glasses were characterized by XRD and EDS,and the corrosion behavior of the metallic glasses was investigated by electrochemical techniques such as polarization curves,AC impedance,and Mott-Schottky curves.It was found that the main components of passivation films formed in sulfuric acid solution are ZrO2 and Al2O3,which showed good passivation ability and high corrosion resistance in sulfuric acid solution under different conditions,performance.Corrosion studies on amorphous samples in different microstructure states show that the as-cast and annealed bulk Zr-based metallic glasses have similar corrosion resistance in sulfuric acid solution,while in the erosion corrosion experiment,the annealed bulk Zr-based metallic glasses show higher corrosion resistance,which is mainly due to the increased hardness of the amorphous alloy after annealing,which reduces the impact of the particles in the solution.Zr-Cu binary metallic glass films can have non-crystalline structure in a wide range of compositional proportions,and its corrosion behavior was studied in 0.01M H2SO4 solution.Through electrochemical tests,it was found that the corrosion resistance of Zr-Cu binary metallic glass films decreases with the increase of Cu content,and its corrosion resistance mainly depends on the coverage of formed ZrO2 passive films on the surface of the alloy.Through XPS analysis,it was found that after immersing in 0.01M H2SO4 solution,the Zr element on the surface of the alloy increases,and when the Cu content is below 50 at.%,the formed Zr02 can cover the entire surface.The above result explains that the competition between the oxidation of Zr atoms(the formation of Zr02 films)and the oxidation-dissolution of Cu atoms plays an important role in the electrochemical behavior of Zr-Cu systems,which determines the microscopic composition of the corroded surface of material.There are many Zr elements in the alloy,the larger of ZrO2 coverage,the better ofcorrosion resistance of the alloy.When the copper content in the alloy is between 70-80 at.%Cu,the Zr-Cu binary system has the best mechanical properties.In addition,the evolution of free volume affects both the mechanical properties and the corrosion behavior of Zr-Cu metallic glass films.It was found that when the Pd content was between 13.0-17.0 at.%in the Pd-Ni-P ternary metallic glass thin film,the alloy could maintain the amorphous structure.The composition of the alloy can be controlled by the electroless plating process,and the increase of the content of Pd(OAc)2 in the bath will promote the increase of the content of P in the film.The corrosion resistance of Pd-Ni-P metallic glass thin films in 3.5%NaCl solution and 0.01M H2SO4 solution increases with the increase of Pd content and P content in the alloy.When the content of Pd in the alloy is high,the Pd-Ni-P metallic glass film has obvious passivation behavior in sodium chloride solution,and with the increase of Pd content,the passivation ability increases.The presence of Pd and P elements was not detected in the Pd-Ni-P metallic glass film by XPS analysis after immersed 72 h in sodium chloride solution,and the surface of alloy was mainly covered by NiO and Ni(OH)2.The results of the study indicate that the chemical composition ratio has a more pronounced effect on the corrosion resistance of metallic glasses.