In-situ high-temperature mechanical property measurement technology and its application in scanning electron microscope

Scanning Electron Microscope (SEM) is an important observational device in scientific research. Over the past decades, scientists have been working on the high temperature deformation measurement and characterization of the critical alloy materials and components in hot sections by in situ observations with SEM. The in situ observations have both important theoretical and high engineering significance in understanding the mechanisms of the microstructure damage evolution of the alloys, understanding their high temperature failure mechanisms, extracting mechanical parameters and improving the accuracy of life prediction methods. However, in situ high temperature measurements in a SEM environment pose major challenges in high efficiency heat source design, establishment of stable high contrast microscopic images, and quantitative measurement of the deformation fields in high temperature environment. New methods and approaches must be therefore developed for measurement of mechanical properties in such harsh environment. In the study presented here, the major difficulties and challenges associated with high temperature experiments implemented in situ SEM are introduced firstly, especially the imaging failure at high temperature. The developments of high temperature in situ SEM technology in recent years are then reviewed, including high temperature in situ test instruments, high temperature imaging technology, and high temperature deformation measurement methods. On this basis, some new research results achieved by our group in the field of creep, fatigue and fracture of nickel based alloy materials at high temperature are introduced, such as the fatigue small and long crack growth behaviors at different temperature as well as in different crystallographic orientations. Nickel based alloy is the critical material for gas turbine and aero-engine due to their excellent creep, fatigue and corrosion resistance at high temperature. Finally, some conclusions of current development in this research field are presented, meanwhile works that need to be further extended in the future are also pointed out.