Pulsed Neutron Imaging Based Crystallographic Structure Study of a Japanese Sword made by Sukemasa in the Muromachi Period

Abstract

Energy-resolved neutron imaging using a pulsed neutron source is capable of visualizing crystallographic information over a large area of a sample by analyzing positiondependent Bragg-edge transmission spectra. We applied this method to a Japanese sword, signed by Sukemasa, to elucidate position dependent crystallographic characteristics, including but not limited to: degree of hardening, crystallite size, degree of preferred orientation. By comparing the degree of hardening to that of a contemporary short Japanese sword (dagger), the Sukemasa showed relatively small changes in the position of Bragg-edge (110) and its broadening. No coarse grain was found within the detector resolution (ca. 1 mm), and the crystallite size of the blade area was analyzed to be almost uniform and less than 1 µm. We thus recognize in a comprehensive manner that the Sukemasa sword was manufactured with great care.

Visualising Martensite Phase Fraction in Bulk Ferrite Steel by Superimposed Bragg-edge Profile Analysis of Wavelength-resolved Neutron Transmission Imaging

“…25) The Braggedge wavelength broadening effect has frequently been used for the analysis and imaging of the martensite phase in ferrite-martensite steel. 3,[5][6][7][26][27][28][29] The crystal structure of α'-martensite is close to that of α-ferrite, and the entire neutron transmission spectral patterns from these microstructures are almost the same. 26) Therefore, a traditional crystalline phase fraction analysis method identifying the spectral patterns [15][16][17][18] cannot be applied to the ferritemartensite phases.…”

“…Hirotaka SATO, 1) * Atsuya KUSUMI, 1) Yoshinori SHIOTA, 2,3) Hirotoshi HAYASHIDA, 4) Yuhua SU, 5) Joseph Don PARKER, 4) Kenichi WATANABE, 6) Takashi KAMIYAMA 1) and Yoshiaki KIYANAGI 1,2) 1) Graduate School of Engineering, Hokkaido University, Kita-13 Nishi-8, Kita-ku, Sapporo, 060-8628 Japan.…”

“…ing from industrial to cultural heritage applications, e.g., the contact surface of an induction-hardened gear, 3) dual phase (DP) and transformation-induced plasticity (TRIP) steels 4) used for automobiles, and the cutting edge of a Japanese sword. [5][6][7] For this reason, martensite has been frequently studied and characterised using electron microscopy, 8) X-ray diffraction 9) and neutron diffraction. 10) Particularly, with respect to the characterisation of a centimetre-sized material for actual use, neutron beam techniques bear the advantage of allowing for the investigation of the bulk-averaged information.…”

“…26) Therefore, previous Bragg-edge imaging studies have successfully conducted the visualisation of ferrite and martensite phases by profiling the small change of a single Bragg-edge wavelength broadening. 3,[5][6][7][26][27][28] Furthermore, as a new approach, Su et al quantitatively estimated the ferrite/martensite phase fraction, which was converted from the average value of crystal lattice plane spacing (d-spacing) distribution evaluated by the conventional single Braggedge profile analysis method. 3) However, the Bragg-edge imaging analysis of the ferrite/ martensite phase fraction exhibits a technical limitation: when both the ferrite and martensite phases are present along the neutron transmission path, the neutron transmission spectrum at the wavelength ranging from approximately 0.405 to 0.415 nm has a superimposed Bragg-edge (sBE) profile owing to both {110} diffraction of the α-ferrite phase, and {110} and {101} diffractions of α'-martensite phase.…”

“…In previous studies, 3,[5][6][7]12,[25][26][27] the Gaussian-type symmetric function with the standard deviation σ 1 has been used for d-spacing distribution functions B 1 (λ − 2d) and D 1 (λ − 2d). Therefore, the Jorgensen-type function was used for both B 0 (λ − 2d hkl ) and B 1 (λ − 2d hkl ) in the present study.…”