EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In the presence of hydrogen (H) donating environments, the strength of high-strength metallic materials is limited by hydrogen-induced embrittlement. Since H embrittlement is caused by the interaction of H with crystal defects such as grain boundaries, dislocations and precipitated second phases, a thorough understanding of these interactions is needed. Atom probe tomography (APT) is a suitable method for the quantitative, near-atomic scale investigation of H at crystal defects, if the H can be preserved at the crystal defects. For the experiments, we used deuterium-(D) as a tracer for H to be able to distinguish it from spurious H present in the APT analysis chamber. The entire sample preparation is at cryogenic temperatures to prevent loss of the D. The samples were charged with D and transferred to a scanning electron microscope (SEM) equipped with a focused ion beam (FIB). Inside the SEM, the sample preparation continues with a FIB lift-out process at cryogenic temperatures. With this method, it is possible to make samples for APT out of a specific D-charged grain boundary. For the transfer from the SEM into the atom probe we used a versatile transfer system that enables cryogenic- or room-temperature-transfer of atom probe specimens. This system can be used to move specimens between cryogenic electro polishing, coating deposition, FIB milling, a modified commercial CAMECA LEAP 4000X HR, and a newly built titanium APT instrument for the direct analysis of H.
The combination of APT with FIB/SEM at cryogenic temperature gives a deeper insight on how hydrogen effects metallic materials and will greatly aide in the rational design of hydrogen resistant materials concepts for the transport and storage of H.