| In recent years,magnesium alloys have attracted much attention and were widely used in land transportation,aerospace,3C products and other fields due to their excellent properties.However,magnesium alloys have poor hardness and corrosion resistance,which severely limits its wide application.Improving the surface properties of magnesium alloys is an important issue in the development and research of magnesium alloys.At present,magnetron sputtering is considered to be one of the best methods for the preparation of surface coating because of its good quality,high density and purity and environment-friendly.Aluminum nitride films were prepared on the surface of AZ91 magnesium alloys by magnetron sputtering.The effects of magnetron sputtering parameters on the properties of the films were studied by orthogonal test and single factor test.The possible relationships among various performance indexes were analyzed and the main factors which influencing the hardness and corrosion resistance of films were studied by analyzing the microstructure of films.Firstly,the degree of influence of magnetron sputtering process parameters(sputtering power,sputtering time,substrate heating temperature,and the ratio of argon / nitrogen gas)on the properties of aluminum nitride film(single properties such as hardness of film,corrosion resistance to simulated body fluid,thickness of film,binding force between film and substrate,surface roughness and the comprehensive properties is mainly based on hardness of film and corrosion resistance)was studied using orthogonal experimental method,and the parameters level combination of the best properties were obtained.It is found that the main process parameters of magnetron sputtering affect the properties of the film in varying degrees,but the order of parameters that affect properties and the level of parameters that correspond to the best properties are not exactly identical,in the range of the values of each parameter.From the point of view that the influence degree of parameters and the optimal value of parameters,there is a certain correlation between the hardness of film and the thickness of film,and the corrosion resistance of film is related to the surface roughness of film.On the basis of orthogonal experiments,single factor experiments were carried out to study the effects of various parameters on the microstructure,hardness andcorrosion resistance of film,the reasons that affect the microstructure and properties are also analyzed.The results show that the change of parameters will affect the physical process of film growth,and change the grain shape,grain size,grain growth speed,grain orientation and surface state of film and then affect the hardness and corrosion resistance of film.Specifically,the change of hardness is mainly related to the preferred crystal orientation(002)of aluminum nitride film,and is also related to the thickness of film.With the increase of sputtering power or sputtering time,the preferred orientation degree of aluminum nitride can be increased and the thickness of film will also be increased which can increase the hardness of film.When the substrate heating temperature increases,although the film thickness increases,it is not favorable for preferred orientation,so it has no definite influence on the hardness of film.For the corrosion resistance of film,the density and thickness of film are the main factors affecting the corrosion resistance of film.When sputtering power is higher,it is easy to cause more hole defects on the surface of film,which is easy to form corrosion channels and then lead to low corrosion resistance.When the sputtering power is lower,the corrosion resistance is also poor for the thickness of film is too thin.When the sputtering temperature is higher or the sputtering time is longer,the dense surface,less roughness and thicker of film can be formed and the corrosion resistance of the film is also better.The larger the ratio of nitrogen to argon,the smaller the film thickness is and the worse the corrosion resistance is. |
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