Integrated in-situ solution for automatic material testing in SEM
In-situ material testing in SEM is a powerful method to investigate the relationship between microstructure of material and its macroscopic mechanical properties. Especially when combined with further analytical techniques such as EDS and EBSD, the response of material microstructure under load can be related to its chemical composition and crystallographic orientations. Such understanding is essential for developing novel materials in a highly efficient way. However, performing in-situ experiment in SEM is a demanding task, especially for new users. The complete in-situ system is usually composed of parts and their corresponding controlling software from different vendors. Trying to coordinate SEM image, mechanical deformation and EDS/EBSD analytics usually involves operating different software or even multiple computers. Moreover, it is entirely up to the user to maintain the correlation between different results. Such intensive manual operation limits typical in-situ experiment to only highly experience user, and only a few deformation steps.
In this contribution, a fully integrated in-situ mechanical test workstation is presented. It combines a mechanical tensile-compression sub-stage, a heating unit, dedicated high temperature SE/BSE detectors and EDS/EBSD analytics into the SEM system. A unified software environment controls all components of the system from a single PC. Furthermore, the system enables unattended automatic in-situ experiment: the user can define multiple region of interests (ROIs), which will be investigated during the automatic workflow. A robust feature tracking and autofocus method is developed to center and focus ROI automatically at each deformation step. Different imaging condition such as scan methods, dwell time and image resolution can be chosen individually for each ROI. EDS/EBSD maps can also be triggered for selected ROIs.
By staining the surface of the specimen with random speckles, high resolution SEM image series during deformation can be used for digital image correlation to obtain microscopic strain distribution. The integrated software can feed the high-resolution SEM images at each deformation step to the GOM correlate software and get the feedback of strain distributions during the in-situ experiment.