Influence Of Microstructure Changes On Damping Properties In Metal Film

Metal film is widely used in the fields of large scale integrated circuits and micro-electromechanical because of its good mechanical properties such as strength,hardness,etc.But recently studies have found that metal,ceramic hard film also has a certain damping capacity,and damping characteristics and mechanism of such films is still to be studied.In this paper the molecular dynamics and multi-scale analysis was adopted,experimental method of scanning electron microscope(SEM),X-ray diffraction(XRD),SEM situ-observation of test systems,mechanical dynamics analyzer and other equipments were used to analyze.The micro-structure changes of metal film defect influence study on damping properties:Copper film with defect was simulated under tensile and impact loading,dislocations and vacancies would appear near the defect,and dislocations would accumulate.To discuss the micro-structure changes of metal film defect influence study on damping properties,the metal film with vacancy,dislocation,twins and porous defects were furthermore studied by the simulation in alternating loading,it shows that:The model with vacancy would appear dislocation near the vacancies and expand forwardly,which consumed mechanical energy;during the relaxation process,the model of embedded dislocation would produce kinks,which slipped away under external loading and extended;dislocation lines vibrated in the weak pinning point and emitted forward after unlocking;in the twins model dislocation would appear at both sides of interface,with the increase of loading the atoms of grain boundaries rearranged,arose dislocation stacking cross boundary,and grain boundary disappeared gradually.The curve of stress-strain and damping factor was obtained according to the endings of simulation,which matched well with the experimental results.The preparation process of metal film influence study on damping properties:the porous aluminum-magnesium alloy film was prepared on substrates by arc ion plating machine under different negative bias.The surface topography,phase analysis and damping properties were detected.It shows that:The number of bigger metal "drop"decreases obviously with the increase of bias pressure and the film micro-holes increase with the increase of bias pressure;In high bias pressure,the grain size of film is smallest and has the best damping properties.It indicates that the damping properties can be improved efficiently by increasing bias pressure on substrates.The micro-structure change of porous metal film influence study on damping properties:The molecular dynamics model was established to simulate vibrations of porous metal film.It shows that:the dislocation shaped in the<110>crystal orientation near the copper film defect,the dislocation can get rid of weak pinning points and limit in the strong pinning points,and emit forward ladder-likely.The internal friction was generated due to the changes of dislocation and the relative sliding near grain boundary,and the stored elastic potential energy was consumed.The results match the damping properties of metal film well.The interface of metal film and substrates influence study on damping properties:The damping properties comparison of porous aluminum-magnesium alloy with stainless steel substrate and single scale porous metal film indicates that the damping properties of cross scale stainless steel substrate is often better than that of single scale porous metal film.For this different,the multi-scale method was adopted to simulate metal film substrate structure,we can find that stress increases bottom-up and from both side to the middle in macroscopic scale;with the increase of loading time,the stress concentration appeared at the tip of micro-defect,the stress changed discontinuously at the interface of film and film-subtract.In microscopic scale,vacancies appeared in the tip of micro-defect continually,further expanded and part of atoms separated.The results show that:The big difference exits between metal film and substrate,which made the changes of the stress,strain and micro-structure discontinuous at interface and micro-defect;the fiction generates between interfaces and damping properties improved overall.The internal changes of dislocation,vacancies and twins,as well as internal fiction energy loss between film and substrate are reasons made damping behavior.It indicates damping properties are affected by microstructure of metal film,which can provide theory evidence for metal film application of the damping vibration in the aerospace fields.