Jacob LaManna2,Youngju Kim1,2,Michael Daugherty1,2,Eli Baltic2,David Jacobson2,Nikolai Klimov2,Caitlyn Wolf2,Ryan Murphy2,Kathleen Weigandt2,Seung Wook Lee3,Wookjin Lee3,Jongyul Kim4,Daniel Hussey2
University of Maryland1,National Institute of Standards and Technology2,Pusan National University3,Korea Atomic Energy Research Institute4
Jacob LaManna2,Youngju Kim1,2,Michael Daugherty1,2,Eli Baltic2,David Jacobson2,Nikolai Klimov2,Caitlyn Wolf2,Ryan Murphy2,Kathleen Weigandt2,Seung Wook Lee3,Wookjin Lee3,Jongyul Kim4,Daniel Hussey2
University of Maryland1,National Institute of Standards and Technology2,Pusan National University3,Korea Atomic Energy Research Institute4
Neutron grating interferometry (nGI) is a unique, nondestructive analysis technique for materials research, providing three forms of image contrast, namely transmission, differential phase, and dark field images. Most notably, the dark field image contrast is generated by the small angle neutron scattering (SANS) of material structure on a length scale, represented by the autocorrelation length (ξ) of the nGI [1]. ξ is proportional to the product of the neutron wavelength and sample-detector distance divided by the interference fringe period. Scanning dark field images over a broad range of ξ allows one to map out the pair correlation function and quantitatively assess the structural parameters of the microstructure such as size, concentration, etc. In this study, we report on the use of neutron grating interferometry (nGI) to ascertain the microstructural properties of steel samples produced by metal additive manufacturing (MAM). The dark-field images generated by nGI on our MAM samples were shown to be sensitive to the microstructure (defects, void, etc). Specifically, the selective laser melted (SLM) SS316 tensile specimens were prepared, and tensile strain was applied perpendicular or parallel to the build direction at three different tensile levels of 0 %, 75 %, and 100 % of fracture. The SS316 compression rods manufactured by SLM and directed energy deposition (DED) methods were prepared with four compression levels of 10 %, 20 %, 30 %, and 40 % of the initial rod length. Two types of nGI setups were used, Far-field interferometer (FFI) and Talbot-Lau interferometer (TLI). The microstructure behavior according to the mechanical deformation of tension and compression that was observed by nGIs can represent the mechanical properties and further predict features such as deformation, fracture, etc. We will present the nGI analysis of these MAM samples to demonstrate how the method can be used to explore hierarchical structures.<br/>[1] Adam J.Brooks et al, Neutron interferometry detection of early crack formation caused by bending fatigue in additively manufactured SS316 dogbones, Materials & Design Volume 140, 15 February 2018, Pages 420-430