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Ishii Akio, Horikawa Keitaro, Hoshino Masato, et al. Strain-field calculation based on X-ray CT images via point matching of impurities using Voronoi diagram. Materialia 36, 102175 (2024); https://doi.org/10.1016/j.mtla.2024.102175., We propose an approach for calculating the strain field inside materials using X-ray computed tomography (CT) images obtained during deformation tests. Our approach is based on the point matching of the detected impurities from the CT images, and the points in the reference and deformed CT images are used to construct a Voronoi diagram. In addition to the change in distance between the reference and deformed points, the volume and shape of the Voronoi polyhdra at each point are used for point matching. By applying the proposed method to a notched Al alloy sample, we calculated the change in the strain field around the notch during deformation in a tensile test using X-ray CT images, and our method was validated.

Ishii Akio, Horikawa Keitaro, Hoshino Masato, et al. Strain-field calculation based on X-ray CT images via point matching of impurities using Voronoi diagram. Materialia 36, 102175 (2024); https://doi.org/10.1016/j.mtla.2024.102175., We propose an approach for calculating the strain field inside materials using X-ray computed tomography (CT) images obtained during deformation tests. Our approach is based on the point matching of the detected impurities from the CT images, and the points in the reference and deformed CT images are used to construct a Voronoi diagram. In addition to the change in distance between the reference and deformed points, the volume and shape of the Voronoi polyhdra at each point are used for point matching. By applying the proposed method to a notched Al alloy sample, we calculated the change in the strain field around the notch during deformation in a tensile test using X-ray CT images, and our method was validated.

Horikawa K., Hino M., Shimizu K., et al. Hydrogen-induced pore formation in Ni–P-plated Al–Zn–Mg alloys revealed by synchrotron X-ray computed tomography and hydrogen detection. International Journal of Hydrogen Energy 82, 801 (2024); https://doi.org/10.1016/j.ijhydene.2024.07.380., The internal microstructures of Ni–P-plated Al–Zn–Mg-based alloys were investigated using synchrotron X-ray computed tomography, together with various analytical methods for hydrogen detection. We clarified that hydrogen-induced pores were generated and segregated near the top and bottom surfaces of a rolled sheet of a commercial-purity Al–Zn–Mg-based alloy with Ni–P plating. In contrast, such segregation of hydrogen micropores was not observed in the high-purity-grade Al–Zn–Mg alloys with Ni–P plating. This result suggests that hydrogen enters the Ni–P plating layer during the plating operation and generates pores in the surface region owing to surface inclusions. Additionally, the hydrogen-induced defects deteriorated the tensile properties such as tensile strength and elongation of the commercial-purity Al–Zn–Mg-based alloys containing higher levels of impurities such as Fe and Si with Ni–P plating.

Horikawa K., Ishii A.. Effect of purity on the internal morphology of blisters on aluminum surfaces. Results in Materials 21, 100522 (2024); https://doi.org/10.1016/j.rinma.2023.100522., This study investigates the effect of purity of aluminum on the morphology of blisters formed on aluminum plates. To this end, aluminum samples with 99 % and 99.99 % purities are prepared, and blisters are generated on the sample surfaces through atmospheric heat treatment. Subsequently, the morphology of blisters on the surface and within the samples are examined using an ion-milling method and field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy. The FE-SEM images reveal that the shape and number density of the blisters vary with the purity of aluminum. The voids under the blisters are spherical when the purity of aluminum is greater than 99.99 % compared to flatter voids when the purity is 99 %. This morphological change is attributed to the local stress caused by neighboring impurity precipitates, and this is theoretically confirmed through Eshelby's ellipsoidal inclusion analysis.