IT-17-IN-3294 Correlative microscopy applied to atom probe specimen preparation – application to selected metallurgical problems

For more than 10 years, site specific specimen preparation for atom probe tomography using FIB and lift out techniques has drastically widened the possible applications of the technique. In particular, it made it possible the preparation of semiconductor or insulator specimen that laser assisted instrument can now analyze almost routinely. FIBs are systemically implanted in SEM chambers, where other imaging devices are also present. In particular, EBSD is now a common equipment in many labs. It provides complementary crystallographic information to SEM surface micrographs, which can be used in different ways. However, very little has been done using these crystallographic information provided by EBSD for APT specimen preparation. In this presentation, we show the various advantages of combining lift out and EBSD techniques, illustrated by different applications from localization of low volume fraction phases (metallographic aspect of EBSD) to ageing under external load and internal interfaces selection, where the orientation of each specific grain is an important parameter. In addition, the preparation of specimens with specific crystal orientation is a new approach to study and control specific experimental artefacts, such as chromatic aberrations, local magnification effect and surface diffusion.
Selected examples in various material science fields will illustrate theses experimental aspects, from carbon redistribution between phases in modern steels, the effect of the crystal orientation on the phase separation under uniaxial load in FeCr model alloys, and the chemical segregation at internal interfaces and defects.