Evaluation of austenite volume fraction in TRIP steel sheets using neutron diffraction

中性子回折を用いたTRIP鋼板中の残留オーステナイト体積率の定量評価

徐 平光   ; 友田 陽*; 新垣 優; Harjo, S.   ; 末吉 仁*

Xu, P. G.; Tomota, Yo*; Arakaki, Yu; Harjo, S.; Sueyoshi, Hitoshi*

The volume fractions of austenite () in TRIP steels were evaluated using time-of-flight neutron diffraction through four methods. They include the analysis method with random texture assumption, the correction method of () peak intensities, the Rietveld refinement method using the summed spectrum without distinguishing the specimen orientations, and the combined Rietveld analysis method for textures and volume fractions. It was found that for a near-random spectrum obtained by the summation of all the measured neutron spectra, the Rietveld refinement provided a satisfactory precision for . Moreover, the precision was further improved through the combined Rietveld analysis method. If the texture measurement is unavailable, it is suggested to measure the neutron spectrum along the transverse direction, and to analyze the using conventional correction method of () peak intensities. It was also confirmed that the increment of evidently improved the combinations of tensile strength and uniform elongation (TSUEl).