0MCDmn1~ Abstract Atom probe tomography (APT) provides direct 3D mappings of constituent elements with near-atomic spatial resolution and is useful for characterizing solute clusters, nano-sized precipitates, solute segregation to dislocation cores, etc. This presentation introduces examples where APT has played a critical role in understanding the microstructural origins of high strength in some metallic alloys in which nanostructure control is critical, e.g., Ni-Co-based superalloys, MgStrain aging is widely used to strengthen the steel and aluminum alloy sheets used in automotive body applications, and elucidation of the strengthening mechanism requires direct observation of the solute-dislocation interaction, which is difficult with TEM. Fig. 1 shows the 3D atom map of Ca superimposed on the BF-TEM image of an originally developed Mg-Al-Zn-Ca-Mn alloy showing a strength increase of 40 MPa by 2% straining and subsequent artificial aging. The correlative TEM/APT analysis convincingly shows that the strength increase is due to dislocation locking by Ca, Al, and Zn segregation and dispersion of a high density of solute clusters.APT also has significant value over analytical TEM in the analysis of light elements, including hydrogen (H). An example is the identification of hydrogen trap sites in pearlitic steel in which the cold deformation simultaneously results in high strength and excellent resistance to hydrogen embrittlement. As shown in Fig. 2, APT analysis of a deformed pearlite charged with deuterium (D), a natural isotope of H, showed D segregation at the cementite/matrix interface, whereas there is no D trapping at the cementite/matrix interface in the undeformed pearlite. This allows us to understand that H trapping delays H accumulation at the crack initiation sites, resulting in excellent resistance to hydrogen embrittlement. Group leader, Nanostructure analysis group, Research Center for Magnetic and Spintronic MaterialsOn the Role of Atom Probe Tomography in Understanding of icrostructural Origin of High Strength in MTaisuke Sasaki is a group leader of the Nanostructure Analysis Group in the Research Center for Magnetic and Spintronic Materials at the National Institute for Materials Science (NIMS), Japan. He received his Ph.D. degree in engineering from the Universityof Tsukuba, Japan, in 2008. His research interests include understanding the structure-property relationship in various metallic materials using scanning electron microscope (SEM), transmission electron microscope (TEM), and three-dimensional atom probe (3DAP). Taisuke Sasaki can be reached by e-mail at Sasaki.Taisuke(CMSM), National Institute for Materials Science (NIMS)Session 2 ｜NIMS Award Symposium 2023Taisuke Sasaki High-temperature Materialsetallic Alloysalloys, and pearlitic steel. Fig. 1. 3D atom map of Ca overlaid BF-TEM image obtained from a strain aged Al-Zn-Ca-Mn alloyFig. 2. 3D atom map of C and D distribution obtained adeformed pearlitic steel20 nm@nims.go.jp.NIMSTalk S2-5100 nm~7 nm from33
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