Title: Time-of-Flight Three Dimensional Neutron Diffraction in Transmission Mode for Mapping Crystal Grain Structures,
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).