Development of on-site measurement technique of retained austenite volume fraction by compact neutron source rans

Abstract

Neutron engineering diffraction is a powerful technique which provides the information of the micro structure of steels in bulk-average, while X-ray diffraction or Electron backscatter diffraction can provide information only from the surface layer. However, such measurement using neutron diffraction is typically performed in a large facility such as a reactor and a synchrotron, while a compact neutron source has never been used for this purpose. Authors have recently developed a neutron diffractometer installed in Riken Accelerator driven compact Neutron Source (RANS) and succeeded in the measurement of texture evolution of a steel sheet. In this study, we made an attempt to measure the volume fraction of retained austenite by RANS. Background noise was carefully eliminated in order to detect as many diffraction peaks as possible with low flux neutrons. The volume fraction was estimated by Rietveld analysis. The accuracy of the measurement result was discussed by comparing with those obtained by a large neutron facility (J-PARC TAKUMI). The volume fraction obtained by RANS with reasonable measurement time, i.e. 30-300 min, showed only 1-2% discrepancies with those obtained in J-PARC. These comparisons suggest that neutron diffraction by RANS is capable of quantitative analysis of the volume fraction of crystal phases, showing the possibility of practical use of an in-house compact neutron source in the industry.