Simultaneous Broadening Analysis of Multiple Bragg Edges Observed by Wavelength-resolved Neutron Transmission Imaging of Deformed Low-carbon Ferritic Steel

With the goal of real-space mapping of dislocation information using a wavelength-resolved (spectroscopic) neutron transmission imaging method, broadenings of multiple Bragg-edges in neutron transmission spectrum were investigated in detail for the first time. Data of time-of-flight (TOF) neutron transmission imaging and diffraction experiments on a polycrystalline low-carbon ferritic steel sample while undergoing tensile testing were analysed. The Bragg-edge neutron transmission spectroscopy was combined with the classical Williamson-Hall method corrected by the crystal elastic anisotropy using the ratio of diffraction Young’s modulus, namely, the corrected classical Williamson-Hall (ccWH) method. As a result, the broadening values evaluated from the ccWH analysis of Bragg-edge data were consistent with results of both our TOF neutron diffraction experiments and previous reports. In addition, it was deduced that the line-broadenings appearing in the plastic deformation condition during tensile testing in our experiment were mainly caused by micro-strain (dislocation density) effect and not by crystallite size effect. Finally, a Bragg-edge broadening mapping method, using a simultaneous multiple Bragg-edges profile analysis based on the ccWH method, could identify plastically deformed zones in the sample more clearly than a traditional single Bragg-edge broadening analysis method.