| Functionally graded films have high-quality characteristics such as ultra-fine,miniature,and high density.Currently,functionally graded films are widely used in aerospace,medical and other fields,and their preparation methods are crucial.Current manufacturing methods for functionally graded thin films mainly include additive manufacturing technologies such as physical vapor deposition and 3D printing.After investigation,it is found that the above technologies have various defects,including:limited material selection range,only one direction of material gradient,large finished product components,poor process repeatability,and the phenomenon of loose and porous materials in the finished product.In view of the above problems,a new method for preparing functionally graded films—radially gradient film preparation methods is proposed.In this thesis,the radial gradient TiNi shape memory alloy thin film is mainly scientifically studied from the following aspects:First,the basic theory and related characteristics of TiNi shape memory alloy were studied,including the characteristics of shape memory effect,superelasticity and martensite transformation,and the radial gradient distribution theory was studied for the multi-directional distribution of functionally graded thin films.Physical deposition model.Next,the magnetron sputtering coating process experiment was completed,the power of the Ti target and Ni target coating,Ar pressure were studied,and the coating rate was further fitted.The sputtering power of the Ni target is 275 W,and the coating rate increases with the increase of the sputtering power,showing a linear distribution.The Ar gas pressure is 0.8Pa,and the rate increases with the Ar gas pressure and then decreases,showing a normal distribution.The coating rate fitted under this sputtering power and Ar gas pressure is 49.9 nm/min;the sputtering power of the Ti target is 275 W,and the coating rate increases with the increase of sputtering power,showing a linear distribution,and the Ar gas pressure is 0.8 Pa,the coating rate increases normally and then decreases with the Ar gas pressure,showing a normal distribution.The coating rate fitted at this sputtering power and Ar gas pressure is 46.0 nm/min.It ensures the characteristics of fast forming speed and good film compactness.Then,the design of the substrate morphology was completed,and the preparation of the morphology substrate(Si)was completed using photolithography and etching techniques.The concentration of the chemical reagent(KOH)and the temperature of the reaction were studied,and the etching rate was fitted.The concentration of the etching solution KOH is 40%,the etching temperature is selected at 80°C,isopropyl alcohol is used as the catalyst,and the etching rate is 850 nm/min.The influencing factors of the surface roughness of the substrate groove were studied,and finally it was found that adding isopropyl alcohol and stirring would promote the reaction better,and a better substrate was obtained.Using the finished film to complete the exploration of the shape memory effect,based on the Kissinger tangent method,the annealing process parameters were determined with the help of XRD and DSC test equipment: annealing temperature500 ℃,annealing time 1h,to ensure that the finished film has a good shape Memory effect.Finally,the UMAT secondary development function of the Abaqus simulation software was used to simulate the deformation of the radial gradient film.Under the same temperature load(20℃～105℃),the deformation was compared with the ordinary homogeneous film,and a new type of film was found.The tip deformation displacement is 1.5 times that of a homogeneous film.Furthermore,the size of the final film is determined,and the film test circuit is designed. |
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