Over the past decade, the improvements in the capability of 3D nanoscale characterization using atom probe tomography (APT) have been remarkable. The advances have enabled the analysis of material systems and structures far beyond the early limitations of APT to bulk metals. In addition, the maturation of FIB-based specimen preparation methods and the use of in-situ (in the FIB) t-EBSD/STEM has made site-specific analyses routine. We will provide an overview of the state-of-the-art hardware, software, and hydrogen applications with a perspective on the performance needs of various selected applications that have moved APT from pure research to the development of new alloys and manufacturing support.

In particular, APT, which is a 3D imaging mass spectrometer with nanoscale spatial resolution and elemental and isotopic mass resolution, is one of the few microscopies that can quantify hydrogen in 3D on the nanoscale. It is a time-of-flight technique that has a high signal-to-noise ratio for masses from hydrogen to uranium and even heavy complex molecular ions. Taking advantage of new, commercially available, vacuum and cryogenic preparation and transfer systems researchers now can study hydrogen in materials directly. Deuterium charged samples may be used to understand the movement of hydrogen within a material to allow alloy development to mitigate embrittlement processes. We will review recent research on this subject with respect to locating hydrogen at grain and phase boundaries as well as segregation to precipitates in high-strength steels. The direct observation of individual Hydrogen atoms in steels and alloys by APT is crucial for the development of Hydrogen-embrittlement-resistant materials [1]. The understanding of hydrogen diffusion processes and the design of trapping sites [2] forms the basis for the development of materials used for the transport and storage of hydrogen.

References
[1] H. Zhao et al., Nature, 2022, 602, 437-441.
[2] Y.-S. Chen et al., Science, 2017, 355, 1196-1199.