Abstract
Over the past decade, wavelength-dependent neutron radiography, also known as Bragg-edge imaging, has been employed as a non-destructive bulk characterization method due to its sensitivity to coherent elastic neutron scattering that is associated with crystalline structures. Several analysis approaches have been developed to quantitatively determine crystalline orientation, lattice strain, and phase distribution. In this study, we report a systematic investigation of the crystal structures of metallic materials (such as selected textureless powder samples and additively manufactured (AM) Inconel 718 samples), using Bragg-edge imaging at the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source (SNS). Firstly, we have implemented a phenomenological Gaussian-based fitting in a Python-based computer called iBeatles. Secondly, we have developed a model-based approach to analyze Bragg-edge transmission spectra, which allows quantitative determination of the crystallographic attributes. Moreover, neutron diffraction measurements were carried out to validate the Bragg-edge analytical methods. These results demonstrate that the microstructural complexity (in this case, texture) plays a key role in determining the crystallographic parameters (lattice constant or interplanar spacing), which implies that the Bragg-edge image analysis methods must be carefully selected based on the material structures.
Highlights
IntroductionDue to its high penetration depth, the neutron is a unique probe for studying the structure of diverse materials (such as functional energy materials) in a non-destructive manner [1,2,3,4]
Due to its high penetration depth, the neutron is a unique probe for studying the structure of diverse materials in a non-destructive manner [1,2,3,4]
(the composition each precipitate availablein in the in the the powder current. isHowever, current study, study, the powder and samples have not been subjected to heat treatment, and were, and additively manufactured (AM) samples have not been subjected to heat treatment, and were, expected to contain less expected to contain less precipitates
Summary
Due to its high penetration depth, the neutron is a unique probe for studying the structure of diverse materials (such as functional energy materials) in a non-destructive manner [1,2,3,4]. Diffraction is based on the interaction between neutrons and the crystal structure in a defined gauge volume that is in the order of cubic millimeters (mm ). Diffraction is based on the interaction between neutrons and the crystal structure in a defined gauge volume that is in the order of cubic millimeters (mm3 ) This enables the characterization of atomic structures of materials, such as the lattice parameter and crystallographic texture. Attenuation-based neutron imaging has been widely adopted to visualize micron-scale structures inside materials (porosity, density inhomogeneity) [11,12,13]. Compared to other imaging techniques such as X-ray imaging, neutron imaging has unique capabilities that allow measurement of bulk components as well as detection of lightweight elements (hydrogen and lithium) [14,15,16]
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