# Time-of-Flight Three Dimensional Neutron Diffraction in Transmission Mode for Mapping Crystal Grain Structures

## TL;DR

This paper introduces ToF 3DND, a non-destructive neutron diffraction technique for 3D microstructure mapping of bulk polycrystalline materials, offering advantages over X-ray methods in size and element sensitivity.

## Contribution

The paper presents a novel ToF 3DND method for 3D grain structure mapping in large, heavy-element samples, with validated reconstruction algorithms and successful application to real samples.

## Key findings

- Reconstructed 108 grains in an iron sample
- Validated algorithms with stacked crystals and EBSD comparison
- Enabled studies of larger samples with complex environments

## Abstract

The physical properties of polycrystalline materials depend on their microstructure, which is the nano-to-centimeter-scale arrangement of phases and defects in their interior. Such microstructure depends on the shape, crystallographic phase and orientation, and interfacing of the grains constituting the material. This article presents a new non-destructive 3D technique to study bulk samples with sizes in the cm range with a resolution of hundred micrometers: time-of-flight three-dimensional neutron diffraction (ToF 3DND). Compared to existing analogous X-ray diffraction techniques, ToF 3DND enables studies of samples that can be both larger in size and made of heavier elements. Moreover, ToF 3DND facilitates the use of complicated sample environments. The basic ToF 3DND setup, utilizing an imaging detector with high spatial and temporal resolution, can easily be implemented at a time-of-flight neutron beamline. The technique was developed and tested with data collected at the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Complex (J-PARC) for an iron sample. We successfully reconstructed the shape of 108 grains and developed an indexing procedure. The reconstruction algorithms have been validated by reconstructing two stacked Co-Ni-Ga single crystals and by comparison with a grain map obtained by post-mortem electron backscatter diffraction (EBSD).