TY - CONF A1 - Evans, Alexander A1 - Sprengel, Maximilian A1 - Ulbricht, Alexander A1 - Kromm, Arne A1 - Werner, Tiago A1 - Sommer, Konstantin A1 - Kelleher, Joe A1 - Mishurova, Tatiana A1 - Serrano Munoz, Itziar A1 - Fritsch, Tobias A1 - Schröder, Jakob A1 - Kannengießer, Thomas A1 - Bruno, Giovanni T1 - Manufacturing a safer world: Diffraction based residual stress analysis for metal additive manufacturing N2 - Metal Additive Manufacturing (AM) technologies such as Laser Powder Bed Fusion (LPBF) are characterized by layer wise construction, which enable advancements of component design, with associated potential gains in performance and efficiency. However, high magnitude residual stresses (RS) are often a product of the rapid thermal cycles typical of the layerwise process. Therefore, a deep understanding of the formation of RS, the influence of process parameters on their magnitude and the impact on mechanical performance is crucial for widespread application. The experimental characterisation of these RS is essential for safety related engineering application and supports the development of reliable numerical models. Diffraction-based methods for RS analysis using neutrons and high energy X-rays enable non-destructive spatially resolved characterisation of both surface and bulk residual stresses in complex components. This presentation will provide an overview of recent research by the BAM at large scale facilities for the characterization of residual stresses in LPBF metallic alloys as a function of process parameters. In addition, the challenges posed by the textured and hierarchical microstructures of LPBF materials on diffraction-based RS analysis in AM materials will be discussed. This will include the question of the d0 reference lattice spacing and the appropriate choice of the diffraction elastic constants (DECs) to calculate the level of RS in LPBF manufactured alloys. T2 - 11th INternational Conference on Residual Stress (ICRS11) CY - Online meeting DA - 28.03.2021 KW - Residual stress analysis KW - Neutron diffraction KW - X-ray diffraction KW - Additive manufacturing KW - Laser powder bed fusion KW - AGIL PY - 2022 AN - OPUS4-54676 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sharatchandra Singh, W. A1 - Stegemann, Robert A1 - Kreutzbruck, Marc A1 - Mukhopadhyay, C. K. A1 - Purnachandra Rao, B. T1 - Mapping of Deformation-Induced Magnetic Fields in Carbon Steels Using a GMR Sensor Based Metal Magnetic Memory Technique N2 - Giant magneto-resistive (GMR) sensor based metal magnetic memory (MMM) technique is proposed for mapping of deformation-induced self-magnetic leakage fields (SMLFs) in carbon steel. The specimens were subjected to different amounts of tensile deformation and the deformation-induced SMLFs were measured using a GMR sensor after unloading the specimens. 3D-nonlinear finite element modeling was performed to predict stress–strain state in a steel specimen under tensile load. The experimentally obtained SMLF images were correlated with the finite element model predicted stress–strain states. Studies reveal that the MMM technique can detect the plastic deformation with signal-to-noise ratio better than 20 dB. The technique enables the mapping of plastic deformation in carbon steels for the evaluation of the severity of deformation. The study also reveals that deformation-induced SMLF is influenced by the presence of initial surface residual stress, introduced by shot peening. The intensity of SMLF signal is found to increase with increase in tensile load and decrease with shot peening. KW - GMR KW - Metal Magnetic Memory KW - 3D-finite element modeling KW - Plastic deformation KW - Carbon steel PY - 2018 DO - https://doi.org/10.1007/s10921-018-0470-8 SN - 0195-9298 VL - 37 IS - 2 SP - 21 PB - Springer US AN - OPUS4-45667 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Charmi, Amir A1 - Falkenberg, Rainer A1 - Ávila, Luis A1 - Mohr, Gunther A1 - Sommer, Konstantin A1 - Ulbricht, Alexander A1 - Sprengel, Maximilian A1 - Saliwan Neumann, Romeo A1 - Evans, Alexander A1 - Skrotzki, Birgit T1 - Mechanical anisotropy of additively manufactured stainless steel 316L: An experimental and numerical study N2 - The underlying cause of mechanical anisotropy in additively manufactured (AM) parts is not yet fully understood and has been attributed to several different factors like microstructural defects, residual stresses, melt pool boundaries, crystallographic and morphological textures. To better understand the main contributing factor to the mechanical anisotropy of AM stainless steel 316L, bulk specimens were fabricated via laser powder bed fusion (LPBF). Tensile specimens were machined from these AM bulk materials for three different inclinations: 0◦, 45◦, and 90◦ relative to the build plate. Dynamic Young’s modulus measurements and tensile tests were used to determine the mechanical anisotropy. Some tensile specimens were also subjected to residual stress measurement via neutron diffraction, porosity determination with X-ray micro-computed tomography (μCT), and texture analysis with electron backscatter diffraction (EBSD). These investigations revealed that the specimens exhibited near full density and the detected defects were spherical. Furthermore, the residual stresses in the loading direction were between −74 ± 24 MPa and 137 ± 20 MPa, and the EBSD measurements showed a preferential ⟨110⟩ orientation parallel to the build direction. A crystal plasticity model was used to analyze the elastic anisotropy and the anisotropic yield behavior of the AM specimens, and it was able to capture and predict the experimental behavior accurately. Overall, it was shown that the mechanical anisotropy of the tested specimens was mainly influenced by the crystallographic texture. KW - Mechanical anisotropy KW - Residual stress KW - Crystal plasticity KW - Selective laser melting (SLM) KW - Laser beam melting (LBM) PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-511719 DO - https://doi.org/10.1016/j.msea.2020.140154 SN - 0921-5093 VL - 799 SP - 140154 PB - Elsevier B.V. AN - OPUS4-51171 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zocca, Andrea A1 - Müller, Bernd R. A1 - Laquai, René A1 - Kupsch, Andreas A1 - Wieder, Frank A1 - Benemann, Sigrid A1 - Wilbig, Janka A1 - Günster, Jens A1 - Bruno, Giovanni T1 - Microstructural characterization of AP40 apatite-wollastonite glass-ceramic N2 - The microstructure of an apatite-wollastonite (code name AP40) glass-ceramic is analyzed in this study by combining 2D microscopy, phase analysis, X-ray absorption and synchrotron X-ray refraction computed tomography (XCT and SXRCT, respectively). It is shown that this combination provides a useful toolbox to characterize the global microstructure in a wide scale range, from sub-micrometer to millimeter. The material displays a complex microstructure comprising a glassy matrix with embedded fluorapatite and wollastonite small crystals. In this matrix, large (up to 200 μm) spike-shaped structures are distributed. Such microstructural features are oriented around a central sphere, thereby forming a structure resembling a sea urchin. A unique feature of SXRCT, in contrast to XCT, is that internal interfaces are visualized; this allows one to show the 3D distribution of these urchins with exceptionally good contrast. Furthermore, it is revealed that the spike-shaped structures are not single crystals, but rather composed of sub-micrometric crystals, which are identified as fluorapatite and diopside phases by SEM-EDX analysis. KW - Glass-ceramic KW - X-ray refraction KW - Computed tomography KW - Microstructure PY - 2023 DO - https://doi.org/10.1016/j.ceramint.2022.12.130 SN - 0272-8842 VL - 49 IS - 8 SP - 12672 EP - 12679 PB - Elsevier Science CY - Amsterdam AN - OPUS4-57452 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ferrari, Bruno A1 - Mishurova, Tatiana A1 - Roveda, Ilaria A1 - Schicchi Said, D. A1 - Darvishi Kamachali, Reza A1 - Evans, Alexander A1 - Agudo Jacome, Leonardo A1 - Serrano-Munoz, Itziar T1 - Microstructural evolution of PBF-LB/M Inconel 718 during solution-aging heat treatments - an in-situ x-ray diffraction study N2 - Inconel 718 (IN718) is a traditional age-hardenable nickel-based alloy that has been increasingly processed by additive manufacturing (AM) in recent years. In the as-solidified condition, IN718 exhibits chemical segregation and the undesired Laves phase, requiring a solution annealing (SA) prior to aging. The material produced by AM does not respond to the established thermal routines in the same way as conventionally produced IN718, and there is still no consensus on which routine yields optimal results. This work aims to provide a fundamental understanding of the heat treatment (HT) response by continuously monitoring the microstructural evolution during SA via time-resolved synchrotron x-ray diffraction, complemented by ex-situ scanning electron microscopy (SEM). The samples were produced by laser powder bed fusion to a geometry of 10x20x90 mm³, from which Ø1x5 mm³ cylindric specimens were extracted. Two different scanning strategies – incremental 67° rotations, Rot, and alternating 0°/67° tracks, Alt – were used, leading to two different as-built conditions. 1-hour SAs were carried out in the beamline ID22 of the ESRF at 50 KeV. Two SA temperatures, SA1 = 1020 °C, and SA2 = 1080 °C were tested for each scanning strategy. Data were processed using the software PDIndexer. In the as-built state, all samples showed typical subgrain columnar cell structures with predominant Nb/Mo segregation and Laves phase at the cell walls, as seen by SEM. The Alt scan induced higher intensity on the Laves peaks than the Rot scan, suggesting a greater content of Laves. Chemical homogenization in the SA was largely achieved during the heating ramp (Fig. 1). SA2 eliminated the Laves peaks just before reaching 1080 °C, and mitigated differences between Rot and Alt samples. On the other hand, SA1 induced the precipitation of the generally detrimental δ phase, also observed by SEM. Furthermore, the Rot scan showed higher δ peak intensities than the Alt scan, indicating a higher content of δ in the latter. No signs of recrystallization were observed in any of the investigated SAs. T2 - FEMS EUROMAT 2023 CY - Frankfurt a. M., Germany DA - 03.09.2023 KW - Additive Manufacturing KW - X-Ray Diffraction KW - Inconel 718 KW - Heat Treatments KW - Microstructure PY - 2023 AN - OPUS4-58392 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ávila Calderón, Luis Alexander A1 - Rehmer, Birgit A1 - Werner, Tiago A1 - Ulbricht, Alexander A1 - Mohr, Gunther A1 - Skrotzki, Birgit A1 - Evans, Alexander T1 - Microstructure Based Study on the Low Cycle Fatigue Behavior of Stainless Steel 316L manufactured by Laser Powder Bed Fusion N2 - Due to the advantages of Laser Powder Bed Fusion (PBF-LB), i.e., design freedom and the possibility to manufacture parts with filigree structures, and the considerable amount of knowledge available for 316L in its conventional variant, the mechanical behavior, and related microstructure-property relationships of PBF-LB/316L are increasingly subject of research. However, many aspects regarding the - application-relevant - mechanical behavior at high temperatures are not yet fully understood. Here, we present the results of an experimental study on the LCF behavior of PBF-LB/316L featuring a low defect population, which makes this study more microstructure-focused than most of the studies in the literature. The LCF tests were performed between room temperature (RT) and 600 °C. The mechanical response is characterized by strain-life curves, and hysteresis and cyclic deformation curves. The damage and deformation mechanisms are studied with X-ray computed tomography, and optical and electron microscopy. The PBF-LB/M/316L was heat treated at 450 °C for 4 h, and a hot‑rolled (HR) 316L variant with a fully recrystallized equiaxed microstructure was tested as a reference. Besides, selected investigations were performed after a subsequent heat treatment at 900 °C for 1 h. The PBF-LB/316L exhibits higher cyclic stresses than HR/316L for most of the fatigue life, especially at room temperature. At the smallest strain amplitudes, the fatigue lives of PBF-LB/M/316L are markedly shorter than in HR/316L. The main damage mechanisms are multiple cracking at slip bands (RT) and intergranular cracking (600 °C). Neither the melt pool boundaries nor the gas porosity have a significant influence on the LCF damage mechanism. The cyclic stress-strain deformation behavior of PBF-LB/M/316L features an initial hardening followed by a continuous softening. The additional heat treatment at 900 °C for 1 h led to decreased cyclic stresses, and a longer fatigue life. T2 - 4th Symposium on Materials and Additive Manufacturing CY - Berlin, Germany DA - 12.06.2024 KW - AGIL KW - 316L KW - Microstructure KW - Low Cycle Fatigue KW - Heat Treatment KW - Laser Poeder Bed Fusion PY - 2024 AN - OPUS4-60432 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Portella, Pedro Dolabella A1 - Ulbricht, Alexander A1 - Evans, Alexander A1 - Altenburg, Simon A1 - Ehlers, Henrik A1 - Hilgenberg, Kai A1 - Mohr, Gunther T1 - Monitoring additive manufacturing processes by using NDT methods N2 - In this presentation we discuss the online monitoring of metallic AM parts produced by the Laser Powder Bed Fusion (LPBF) process by using optical, thermographic and electromagnetic methods. In a first approach we present the detection of defects generated during the process and discuss how to improve these methods for the optimization of design and production of metallic AM parts. T2 - ABENDI - Workshop CY - Online meeting DA - 19.11.2020 KW - Additive Fertigung PY - 2020 AN - OPUS4-52042 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Trappe, Volker A1 - Kraus, David A1 - Kübler, Stefan A1 - Eisermann, René T1 - Multiaxial fatigue damage of glass fiber reinforced polymers N2 - Fiber reinforced polymers (FRPs) are a well established material in lightweight applications, e.g. in automotive, aerospace or wind energy. The FRP components are subjected to multiaxial mechanical as well as hygrothermal loads. Common operation temperatures are in the range of 213 K and 373 K (-60 °C and 100 °C) at a relative humidity of 10% to 90%. In spacecraft applications, the environmental conditions are even more extreme. However, the correlation between multiaxial mechanical loading and harsh environment conditions have to-date not been investigated in detail. The project aims to investigate the fatigue behavior of FRPs dependent on multiaxial mechanical loading, temperature, and humidity. Extensive experimental testing is performed on flat plate and cylindrical tube specimens, accompanied by numerical and analytical calculations. T2 - 24. Nationales SAMPE Symposium CY - Dresden, Germany DA - 06.02.2019 KW - Composite KW - Fatigue KW - Thermomechanics KW - Distributed fiber optic sensors PY - 2019 AN - OPUS4-47335 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Usmani, Shirin A1 - Stephan, Ina A1 - Huebert, Thomas A1 - Kemnitz, E. T1 - Nano metal fluorides for wood protection against fungi N2 - Wood treated with nano metal fluorides is found to resist fungal decay. Sol−gel synthesis was used to synthesize MgF2 and CaF2 nanoparticles. Electron microscopy images confirmed the localization of MgF2 and CaF2 nanoparticles in wood. Efficacy of nano metal fluoride-treated wood was tested against brown-rot fungi Coniophora puteana and Rhodonia placenta. Untreated wood specimens had higher mass losses (∼30%) compared to treated specimens, which had average mass loss of 2% against C. puteana and 14% against R. placenta, respectively. Nano metal fluorides provide a viable alternative to current wood preservatives. KW - Brown-rot fungi KW - Coniophora puteana KW - Fluoride nanoparticles KW - Fluorolytic sol−gel KW - Rhodonia placenta KW - SEM wood characterization KW - Wood protection PY - 2018 DO - https://doi.org/10.1021/acsanm.8b00144 SN - 2574-0970 VL - 2018 SP - 1 EP - 6 PB - American Chemical Society (ACS) CY - Washington DC, US AN - OPUS4-44730 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fritsch, Tobias A1 - Sprengel, Maximilian A1 - Evans, Alexander A1 - Farahbod-Sternahl, L. A1 - Saliwan Neumann, Romeo A1 - Hofmann, M. A1 - Bruno, Giovanni T1 - On the determination of residual stresses in additively manufactured lattice structures N2 - The determination of residual stresses becomes more complicated with increasing complexity of the structures investigated. Additive manufacturing techniques generally allow the production of ‘lattice structures’ without any additional manufacturing step. These lattice structures consist of thin struts and are thus susceptible to internal stress-induced distortion and even cracks. In most cases, internal stresses remain locked in the structures as residual stress. The determination of the residual stress in lattice structures through nondestructive neutron diffraction is described in this work. It is shown how two difficulties can be overcome: (a) the correct alignment of the lattice structures within the neutron beam and (b) the correct determination of the residual stress field in a representative part of the structure. The magnitude and the direction of residual stress are discussed. The residual stress in the strut was found to be uniaxial and to follow the orientation of the strut, while the residual stress in the knots was more hydrostatic. Additionally, it is shown that strain measurements in at least seven independent directions are necessary for the estimation of the principal stress directions. The measurement directions should be chosen according to the sample geometry and an informed choice on the possible strain field. If the most prominent direction is not measured, the error in the calculated stress magnitude increases considerably. KW - Additive manufacturing KW - Laser powder bed fusion KW - Residual stress KW - Principal stress components KW - Neutron diffraction KW - Lattice structures PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520663 DO - https://doi.org/10.1107/S1600576720015344 SN - 1600-5767 VL - 54 SP - 228 EP - 236 AN - OPUS4-52066 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -