Insights from Quasi-in situ Cryogenic-Transfer Atom Probe Tomography for Analyzing Hydrogen Diffusion in Metallic Alloys

Cryogenic-transfer atom probe tomography (APT) has emerged as a powerful technique for nanoscale compositional analysis of hydrogen segregation in materials, offering critical insights into hydrogen embrittlement mechanisms. However, accurate quantification of hydrogen concentration in materials requires careful handling of sample exposure during the cryogenic transfer-APT process. Therefore, we describe the quantitative changes in the surface composition of hydrogen and oxygen in an austenitic FeCrNi model alloy during the ultrahigh vacuum transfer using the state-of-the-art LEAP 6000 XR APT, employing both deep UV laser-assisted and voltage pulsed modes of analysis. These insights were applied to interpret deuterium desorption from the FeCrNi alloy at room temperature after electrochemical deuterium-charging. The findings underscore the importance of managing sample exposure throughout the cryogenic-transfer APT process and introduce a novel quasi-in situ approach to analyzing hydrogen out-diffusion kinetics, which could be extended to a broader range of metallic alloys.