Grain morphology reconstruction of crystalline materials from Laue three-dimensional neutron diffraction tomography

Stavros Samothrakitis,Markus Strobl,Christian Grünzweig,Marc Raventós,Marina Garcia-Gonzalez,Camilla Buhl Larsen,Jaromír Kopeček,Michael Tovar,Søren Schmidt,Jan Čapek

doi:10.1038/s41598-020-60330-w

Abstract

The macroscopic properties of advanced engineering and functional materials are highly dependent on their overall grain orientation distribution, size, and morphology. Here we present Laue 3D neutron diffraction tomography providing reconstructions of the grains constituting a coarse-grained polycrystalline material. Reconstructions of the grain morphology of a highly pure Fe cylinder and a Cu cube sample are presented. A total number of 23 and 9 grains from the Fe and Cu samples, respectively, were indexed and reconstructed. Validation of the grain morphological reconstruction is performed by post-mortem EBSD of the Cu specimen.

Highlights

The assessment of the grain structure of polycrystalline samples can be performed using a combination of diffraction and imaging approaches with electrons[3,4], X-rays[5,6,7,8] and neutrons[9,10,11]
The results proof the ability of Laue 3D Neutron Diffraction Tomography to provide 3D reconstructions of the grain network constituting a polycrystalline sample
The number of grains reconstructed per volume in the iron sample matches the one reported for the ToF method, and both exceed the one reported for neutron diffraction tomography

Summary

Introduction

The assessment of the grain structure of polycrystalline samples can be performed using a combination of diffraction and imaging approaches with electrons[3,4], X-rays[5,6,7,8] and neutrons[9,10,11]. The 3D grain morphology reconstruction tackles the geometrical challenge of a non-conventional tomographic reconstruction, under the simplification that the shape of the peaks identified to belong to an individual grain is dependent only on the grain geometry It is shown, that Laue 3DNDT is able through relatively short exposures and intense computing to obtain the crystal grain positions, orientations and morphology of coarse-grained materials. The intensity of a Laue peak projection does not comply to a description as simple as the Beer Lambert law, but depends, among others, on the deflected wavelength in an undefined spectrum, the volume and shape of the grain, the structure factor of the reflecting (hkl) plane, the temperature of the sample, the mosaicity, the attenuation of the beam and the local efficiency of the detection system (which in a transmission experiment can be accounted for much easier). For each individual grain the corresponding peaks, their shapes and intensity distributions and the diffraction geometry, i.e. orientation of the grain and related projection angle in 3D, are well known

Methods

Results

Conclusion