Analysis and Mapping of Detailed Inner Information of Crystalline Grain by Wavelength-Resolved Neutron Transmission Imaging with Individual Bragg-Dip Profile-Fitting Analysis

Abstract

As a new method for evaluating single crystals and oligocrystals, pulsed neutron Bragg-dip transmission analysis/imaging method is being developed. In this study, a single Bragg-dip profile-fitting analysis method was newly developed, and applied for analyzing detailed inner information in a crystalline grain position-dependently. In the method, the spectrum profile of a single Bragg-dip is analyzed at each position over a grain. As a result, it is expected that changes in crystal orientation, mosaic spread angle and thickness of a perfect crystal can be evaluated from the wavelength, the width and the integrated intensity of the Bragg-dip, respectively. For confirming this effectiveness, the method was applied to experimental data of position-dependent Bragg-dip transmission spectra of a Si-steel plate consisting of oligocrystals. As a result, inner information of multiple crystalline grains could be visualized and evaluated. The small change in crystal orientation in a grain, about 0.4°, could be observed by imaging the Bragg-dip wavelengths. By imaging the Bragg-dip widths, both another grain and mosaic block in a grain were detected. Furthermore, imaging results of the integrated intensities of Bragg-dips were consistent with the results of Bragg-dip width imaging. These small crystallographic changes have not been observed and visualized by previous Bragg-dip analysis methods.

Microstructural Characterization of a Single Crystal Copper Rod Using Monochromatic Neutron Radiography Scan and Tomography: A Test Experiment

“…In case large size single crystal grains are present within a sample, the wavelength scan analysis of the areas in which they are present shows an intensity attenuation profile, which is affected by the strong scattering effect of a few selected neutron wavelengths interacting with the specifically oriented lattice planes of the single crystal. Since such single crystal areas only interact with specific neutron wavelengths, the transmitted beam exhibits an almost flat profile showing the presence of dips at specific wavelengths corresponding to the Bragg scattering conditions of the lattice planes, according to their 2θ orientation with respect to the primary beam direction [10][11][12][13][14].…”

Special Issue Advances in Neutron Imaging

“…Eleven publications report about very different topics from the application of neutron imaging, starting with an instrument at the NEUTRA facility (Switzerland) using neutrons and X-rays that was reported [1], followed by the work of the Australian imaging group, which presented new mathematical methods for reconstructing strain from energy-resolved neutron images [2]. The Swiss imaging group made a second contribution, investigating the mapping of the spatial distribution of pores using neutron microtomography [3], and from Japan a new method was presented dealing with the inner information of crystalline grain realized by wavelength-resolved neutron imaging [4].…”