Microstructure Distribution of Japanese Sword Cross Sections Analyzed by the Diffractometer TAKUMI at J-PARC

Abstract

Four cross sections of Japanese swords produced in different ages and regions were measured with neutron diffraction to obtain information about the manufacturing process. Time-of-flight engineering diffractometer TAKUMI at J-PARC was used to elucidate position-dependent crystallographic characteristics, such as quenching depth, degree of texture, crystallite size, and microstrain in an mm scale by using the Rietveld refinement program and sample broadening analysis implemented in MAUD. The position-dependent carbon content estimated from the phase fraction of the secondary phase showed qualitatively good agreement with those obtained by the spark-OES and EPMA analysis conducted in the mid-1980s in Japan. On the other hand, carbon contents estimated by the tetragonality (c/a ratio) in the martensite phase are obviously low. Crystallite size and microstrain are very similar in the four samples, regardless of any differences in the age and area of production.