Development Of Quantitative Double-tilt In Situ Compression Technology For Transmission Electron Microscope

Compressive stress is an important service load of materials.Studying the evolution law of microstructure of materials under compressive stress is helpful to establish the relationship between microstructure and mechanical properties of materials,which will provide important scientific support for the design and performance optimization of new materials.Transmission electron microscopy(TEM)is one of the most important methods to study the microstructure of materials at the scale of nanometer to subangstroms.It is an effective way to establish the correlation between microstructure and mechanical properties by introducing compressive stress field into TEM and in situ studying the evolution of microstructure of materials under compressive stress.Instrument companies such as Hysitron,Nano Factory and Zeptools Technology have developed different types of in-situ compression stress test devices for transmission electron microscopy.By using a precision piezoelectric ceramic built into the back end of the sample rod,the diamond indenter at the front end of the sample rod is driven to carry out precise movement on the sub-nanometer scale.Furthermore,the integration of microstructure and mechanical properties of materials can be realized to a certain extent.These scientific instruments provide important technical methods for studying the elastic-plastic deformation mechanism of materials.However,due to the large size of the drive and sensing system,the double-tilt of the sample on the ? and ? axis is restricted,which causes the defects such as dislocation of samples cannot be tilted to the best imaging contrast,which reduces the resolution and effectiveness of the observation of microstructure evolution.In order to solve the problems of the above platforms,a quantitative double-tilt in-situ compression platform for transmission electron microscope have been developed.The specific work is as follows:The double-tilt mechanical platform developed in this paper adopts a micro piezoelectric ceramic for mechanical loading,a MEMS integrated piezoresistive mechanical sensor for mechanical measurement and sample loading,and a flexible circuit board for stable signal transmission.Through proper lead design and connection,quantitative compression of the sample during the double-tilt process is realized.After the platform was built,the stability of the driver was tested and the sensitivity of the sensor was calibrated.The quantitative in-situ compression experiments of Ni nanopillar were carried out on the calibrated platform,and the quantitative compression of the sample during the TEM double-tilt process was realized.The stress-strain curves during the compression process were obtained.Through the improved design of the flexible circuit board and the optimization of the platform,the measured resolution of the mechanical sensor reaches 8 ?N and 8 nm.In addition,the stress and strain data can be collected by observing TEM images to obtain higher mechanical resolution.The two quantitative methods are integrated in the same platform,which can meet the vast majority of experimental needs.