Preparation And Damping Capacity Of Ti-Ta-Zr-Fe Shape Memory Alloy Thin Films

With properties such as combination of temperature and stress perception,and driving performance as well as tiny specific surface area,high output power and various advantages of bulk materials,SMA films obtain a broad application prospect in the field of microelectromechanical.However,researches on damping capacity of SMA thin films have rarely been reported.Ti-Ta-Zr-Fe SMA films were prepared by DC magnetron sputtering.The effects of sputtering parameters on chemical composition and surface morphology of the films were studied by atomic force microscopy and scanning electron microscopy,and the process parameters were optimized.X ray diffraction analysis and transmission electron microanalysis were used to study the influence of different Fe content on phase composition and microstructure of the films.Reverse martensitic phase transition temperatures were measured by the bending method.Damping capacity of the film was studied by dynamic thermo mechanical analysis.The mechanical properties of the film were studied by tensile test and nano indentation.It was found that with the increase of sputtering power,the content of Ti in the film increased first and then decreased,while the content of Ta and Zr decreased first and then increased.The surface roughness of the film increased first and then decreased.With the increase of Ar working pressure,the Ti content in the films decreased,the Ta content increased,and the Zr content decreased first and then increased.The surface roughness increased with the increase of working pressure.Sputtering power 200 W,Ar working pressure 0.15 Pa,time 120 min was the optimized process parameters.According to the analysis of the microstructure,the room temperature phase composition of the alloy films with different Fe content was both the parent phase and the martensite phase.The phase transition temperature decreased with the increase of Fe content in the films.The intensity ratio of parent phase and martensite phase in XRD spectrum increased.The microstructure of the films with different Fe content was nanocrystalline grain size of 30nm~60nm,and the grain size decreased with the increase of Fe content.Martensitic lath were visible in the grains.By testing the damping capacity,it was found that with the increase of frequency,the temperature of the damping peak moved to high temperature direction with increasing.The damping peaks during cooling process were higher compare to heating process.Temperature ranges with damping peaks which were higher than 0.04 were quite wide.When the frequency is 20 Hz,the damping capacity of the film containing 0.3at.%,0.6at.%,1.0at.%Fe respectively could reach 0.078,0.094 and 0.116.The strain amplitude had no influence on the damping capacity of the film.The increase of Fe content lead to higher damping capacity and higher storage modulus.IF were above 0.04 between-15℃ and 75℃ so they were considered as films with high damping capacity in broad temperature range.Because of the small grain size and plenty of grain boundaries,the mechanism of film damping was grain boundary relaxation.The mechanical properties test showed that the addition of Fe improved the plasticity and strength of the films simultaneously.With the increase of Fe content,the tensile fracture stress and tensile fracture strain of the films was enhanced.The modulus and hardness of the film were also strengthened.The fracture stress and fracture strain of the films containing 1.0at.% Fe was 657 MPa and 12.8% respectively.This was because the grain size decreased with the increase of Fe content,and the strengthening effect of fine grain was reinforc ed.