Mechanical Properties Of TiNi Shape Memory Alloy At Micro-nano Scale

Micro electro mechanical system(MEMS)technology not only shows great potential application prospect but also presents a series of challenges to people.Firstly,due to the extremely small physical size of micro-nano scale materials,traditional methods of preparation,testing and characterization are no longer effective for these materials.Secondly,materials or devices under the micro-nano scale will show a strong size effect,and their related optical properties,thermal properties and mechanical properties are greatly different from those under the macroscopic conditions.Shape memory alloy(SMA)is a kind of intelligent material that integrates perception and drive.Not only does it have high energy density,high drive frequency,large output stress and strain,but also outstanding comprehensive properties and strong potential for miniaturization.This research use focused ion beam-electron beam double beam equipment(FIB/SEM)as platform for processing and characterization.Under the objective conditions that the equipment does not have mechanical sensors,the research innovatively put forward a test method to measure the elastic coefficient of the shape memory alloy cantilever structure,which is based on the contact deformation,and there are related calculation model can be further applied to calculate the young's modulus of shape memory alloy.The focused ion beam has a certain convergence Angle.The beam structure prepared by the top-down etching method will have a taper of 1° to 4°.In this study,a 19.22 ?m long non-taper Ti Ni shape memory alloy cantilever beam structure was prepared by horizontal etching method.In this study,an orthogonal test was designed to study the influence of four process parameters on the surface roughness of the deposited samples in the process of focused ion beam chemical vapor deposition(FIB-CVD): ion beam current,ion beam spot diameter,single point irradiation time and irradiation time interval.According to the optimum process parameters obtained by the orthogonal experiment,namely: ion beam current 1 p A,irradiation time interval 0.2 ?s,single point irradiation time 0.1 ?s,and ion beam spot diameter 11 nm,the micron column with diameter 1?m and height 15.3 ?m was prepared,and its surface roughness was 57.3 nm.In this study,through ANSYS simulation,the influence law of the diameter of the micron column on the shear stress at the deposition bonding position and the influence law of the length of the micron column on the deformation of the stressed end were studied.The simulation results showed that the increase of the diameter and the increase of the micron column can effectively improve the reliability of the testing tool of the micron column.Through the heat recovery experiment,this study measured the thermal recovery starting temperature of the shape memory alloy is between 50 ? to 60 ?,which is higher than that at macroscopic scales.When the environment temperature is higher than the initial temperature but lower than 100 ?,the plastic deformation of the micron column is partially restored,and the ambient temperature for the complete recovery of the micron column is between 100 ? to 120 ?.