TY - JOUR A1 - Ávila Calderón, Luis Alexander A1 - Graf, B. A1 - Rehmer, Birgit A1 - Petrat, T. A1 - Skrotzki, Birgit A1 - Rethmeier, Michael T1 - Characterization of Ti-6Al-4V fabricated by multilayer laser powder-based directed energy deposition N2 - Laser powder-based directed energy deposition (DED-L) is increasingly being used in additive manufacturing (AM). As AM technology, DED-L must consider specific challenges. It must achieve uniform volume growth over hundreds of layers and avoid heat buildup of the deposited material. Herein, Ti–6Al–4V is fabricated using an approach that addresses these challenges and is relevant in terms of transferability to DED–L applications in AM. The assessment of the obtained properties and the discussion of their relationship to the process conditions and resulting microstructure are presented. The quality of the manufacturing process is proven in terms of the reproducibility of properties between individual blanks and with respect to the building height. The characterization demonstrates that excellent mechanical properties are achieved at room temperature and at 400 °C. KW - AGIL KW - Laser powder-based directed energy deposition KW - Tensile properties KW - Ti-6Al-4V KW - Microstructure PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-542262 SN - 1438-1656 SN - 1527-2648 SP - 1 EP - 15 PB - Wiley-VCH CY - Weinheim AN - OPUS4-54226 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rockenhäuser, Christian A1 - Schriever, Sina A1 - von Hartrott, P. A1 - Piesker, Benjamin A1 - Skrotzki, Birgit T1 - Comparison of long-term radii evolution of the S-phase in aluminum alloy 2618A during ageing and creep N2 - A study was made on the effect of creep loading on the precipitate radii evolution of the aluminum alloy 2618A. The overageing process of the alloy was investigated under load at a temperature of 190 °C with stresses between 79 and 181 MPa and compared to stress free isothermal ageing. The precipitates responsible for strength were characterized using dark-field transmission electron microscopy (DFTEM). This allows the experimental Determination of radii distributions of the rod-shaped Al2CuMg precipitates and the evaluation regarding their mean precipitate radius. It was found that the mean precipitate radius enables the comparison of the different microstructural conditions of crept and uncrept samples. The mean precipitate radii of the samples experiencing creep are significantly higher than those of undeformed samples. It was shown that the acquired radii distributions are viable to determine averaged particle radii for comparison of the aged samples. A ripening process including pipe diffusion along dislocations describes the data on coarsening very well for the creep samples. KW - Aluminum alloys KW - Electron microscopy KW - Aging KW - Creep KW - Microstructure KW - S-Phase PY - 2018 U6 - https://doi.org/10.1016/j.msea.2018.01.033 SN - 0921-5093 VL - 716 SP - 78 EP - 86 PB - Elsevier B. V. AN - OPUS4-44090 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scheuerlein, C. A1 - Andrieux, J. A1 - Michels, M. A1 - Lackner, F. A1 - Chiriac, R. A1 - Hagner, M. A1 - Di Michiel, M. A1 - Meyer, Christian A1 - Toche, F. ED - Foley, C. P. T1 - Effect of the fabrication route on the phase and volume changes during the reaction heat treatment of Nb3Sn superconducting wires N2 - Accelerator magnets that can reach magnetic fields well beyond the Nb-Ti performance limits are presently being built and developed, using Nb3Sn superconductors. This technology requires reaction heat treatment (RHT) of the magnet coils, during which Nb3Sn is formed from its ductile precursor materials (a “wind and react” approach). The Nb3Sn microstructure and microchemistry are strongly influenced by the conductor fabrication route, and by the Phase changes during RHT. By combining in situ differential scanning calorimetry, high Energy synchrotron x-ray diffraction, and micro-tomography experiments, we have acquired a unique data set that describes in great detail the phase and microstructure changes that take place during the processing of restacked rod process (RRP), powder-in-tube (PIT), and internal tin (IT) Nb3Sn wires. At temperatures below 450 ° the phase evolutions in the three wire types are similar, with respectively solid state interdiffusion of Cu and Sn, Cu6Sn5 formation, and Cu6Sn5 peritectic transformation. Distinct differences in phase evolutions in the wires are found when temperatures exceed 450 °C. The volume changes of the conductor during RHT are a difficulty in the production of Nb3Sn accelerator magnets. We compare the wire diameter changes measured in situ by dilatometry with the phase and void volume evolution of the three types of Nb3Sn wire. Unlike the Nb3Sn wire length changes, the wire diameter evolution is characteristic for each Nb3Sn wire type. The strongest volume increase, of about 5%, is observed in the RRP wire, where the main diameter increase occurs above 600 °C upon Nb3Sn formation. KW - Nb3Sn KW - Microstructure KW - Phase transformations KW - Volume changes KW - X-ray diffraction KW - Differential scanning calorimetry KW - Synchrotron micro-tomography PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-505128 VL - 33 IS - 3 SP - 034004 PB - IOP Publishing CY - Bristol (UK) AN - OPUS4-50512 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rockenhäuser, Christian A1 - Rowolt, C. A1 - Milkereit, B. A1 - Darvishi Kamachali, Reza A1 - Kessler, O. A1 - Skrotzki, Birgit T1 - On the long-term aging of S-phase in aluminum alloy 2618A N2 - The aluminum alloy 2618A is applied for engine components such as radial compressor wheels which operate for long time at elevated temperatures. This results in coarsening of the hardening precipitates and degradation in mechanical properties during the long-term operation, which is not taken into account in the current lifetime prediction models due to the lack of quantitative microstructural and mechanical data. To address this issue, a quantitative investigation on the evolution of precipitates during long-term aging at 190 °C for up to 25,000 h was conducted. Detailed transmission electron microscopy (TEM) was combined with Brinell hardness measurements and thorough differential scanning calorimetry (DSC) experiments. The results showthat GPB zones and S-phase Al2CuMg grow up to < 1,000 h during which the GPB zones dissolve and S-phase precipitates form. For longer aging times, only S-phase precipitates coarsen, which can be well described using the Lifshitz–Slyozov Wagner theory of ripening. A thorough understanding of the underlying microstructural processes is a prerequisite to enable the integration of aging behavior into the established lifetime models for components manufactured from alloy 2618A. KW - Long-term aging KW - Transmission electron microscopy (TEM) KW - Differential scanning calorimetry (DSC) KW - Microstructure KW - S-phase KW - Ostwald ripening PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-519899 SN - 0022-2461 VL - 56 IS - 14 SP - 8704 EP - 8716 PB - Springer Nature AN - OPUS4-51989 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - von Hartrott, P. A1 - Metzger, M. A1 - Rockenhäuser, Christian A1 - Skrotzki, Birgit T1 - Lifetime assessment of aging materials N2 - Materials subjected to high-temperature service conditions will change their microstructure with time. Associated with this aging process is a change of mechanical properties as well as a change of damage mechanisms. Within the scope of the FVV project Aging and Lifetime, Fraunhofer IWM in Freiburg and BAM in Berlin (both Germany) experimentally characterized the widespread high-temperature aluminum alloy EN AW-2618A in different overaging states. Based on the experimental findings, models for numerical lifetime assessment with the finite-element method were implemented. KW - Aluminum alloy KW - Aging KW - Microstructure KW - Lifetime prediction KW - Damage PY - 2018 U6 - https://doi.org/10.1007/s38313-018-0084-7 SN - 2192-9114 VL - 79 IS - 10 SP - 64 EP - 68 PB - Springer AN - OPUS4-46065 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 U6 - 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 - JOUR A1 - Rodrigues, A. C. P. A1 - Feller, A. A1 - Agudo Jácome, Leonardo A1 - Azevedo, C. R. F. T1 - Use of synthetic Fe3O4-rich tribofilms to investigate the effect of microconstituents, temperature and atmosphere on the friction coefficient during pin-on-disc tribotest N2 - This work investigates the effect of the tribotesting parameters (temperature, atmosphere, and third body chemical composition) on the coefficient of friction (CoF) during pin-on-disc dry (PoD) sliding tribotests using artificial third bodies. The third body comprised nanometric Fe3O4-based binary to quaternary chemical compositions containing copper, graphite, and zirconia. These mixtures were manually or ball-milled prepared, and pin-on-disc tribotests were conducted at 23 °C and 400 °C under air or nitrogen atmospheres. Combining PoD and artificial third body to create synthetic tribofilms might be useful for testing new formulations of Cu-free friction materials. Microstructural characterisation of the tribofilms was used to study the stability of the Fe3O4, copper, and graphite nanoparticles under different testing conditions to understand their effects on the CoF. For the Fe3O4-C-ZrO2-X systems, the ball milling mixing promoted the formation of turbostratic graphite in the tribofilm, impairing the lubricating effect of the graphite under air atmosphere at 23 °C. The formation of monoclinic CuO in the tribofilms during tribotests at 400 °C under air and N2 atmospheres promoted a lubricating effect. KW - Tribology KW - Microstructure KW - Oxide KW - Transmission electron microscopy PY - 2022 U6 - https://doi.org/10.1088/2051-672X/ac9d51 SN - 2051-672X VL - 10 IS - 4 SP - 044009-1 EP - 044009-18 PB - IOP Pobilishing AN - OPUS4-56467 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Suárez Ocano, Patricia A1 - Fries, S. G. A1 - Lopez-Galilea, I. A1 - Darvishi Kamachali, Reza A1 - Roik, J. A1 - Agudo Jácome, Leonardo T1 - The AlMo0.5NbTa0.5TiZr refractory high entropy superalloy: Experimental findings and comparison with calculations using the CALPHAD method N2 - Detailed microstructural characterization of the AlMo0.5NbTa0.5TiZr refractory high entropy superalloy in the as-cast state is reported for first time and compared with the state annealed at 1400 oC for 24 h. The former shows a dendritic structure, with a mixture of A2/B2 phases < 20 nm in both the dendritic and interdendritic regions. A mostly amorphous phase, rich in Al and Zr, is found within the interdendritic region. The annealed state reproduced the combination of A2/B2/Al-Zr-rich phases reported previously. Calculations from two relevant ThermoCalc databases were compared with the experimental results. Equilibrium calculations were compared with results for the annealed alloy, whereas solidification paths calculated using Scheil-Gulliver model were used for comparison with the as-cast alloy. A previously hypothesized spinodal decomposition during cooling as the mechanism responsible for the patterned A2/B2 microstructure is confirmed via the CALPHAD calculations, pointing to its use as an efficient design tool for such alloys. Finally, the comparison between the experimental and computational findings allowed better understanding the solidification path and equilibrium stability of this alloy, giving a base to make better decisions on the field of new refractory superalloy design. KW - CALPHAD database analysis KW - Refractory superalloys KW - Chemically complex alloy KW - Characterization KW - Microstructure PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-545906 SN - 1873-4197 VL - 217 SP - 1 EP - 13 PB - Elsevier CY - Amsterdam AN - OPUS4-54590 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kingsbery, Phillip A1 - Stephan-Scherb, Christiane T1 - Effect of KCl deposits in high‐temperature corrosion on chromium‐rich steels in SO2‐containing atmosphere N2 - High‐temperature corrosion was studied under multiple chemical loads on ferritic‐austenitic model alloys (Fe–13Cr, Fe–18Cr–12Ni, and Fe‐25Cr–20Ni) with KCl deposit under 0.5% SO2/99.5% Ar gas atmosphere at 560°C. Postexposure characterization was done by X‐ray diffraction and scanning electron microscopy. In a pure SO2/Ar environment a protective Cr2O3 scale was formed by all samples. The introduction of KCl deposits causes the scale to be nonprotective and multilayered, consisting of CrS, FeS, Cr2O3, Fe3O4, and Fe2O3. The impact of the microstructure and alloying elements is discussed. KW - High‐temperature corrosion KW - KCl KW - Microstructure KW - SO2 KW - Steel alloy PY - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-543056 VL - 73 IS - 5 SP - 758 EP - 770 PB - Wiley-VCH CY - Weinheim AN - OPUS4-54305 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ginés-Palomares, J.-C. A1 - Fateri, M. A1 - Schubert, T. A1 - de Peindray d’Ambelle, L. A1 - Simon, Sebastian A1 - Gluth, Gregor A1 - Günster, Jens A1 - Zocca, Andrea T1 - Material aspects of sintering of EAC-1A lunar regolith simulant N2 - Future lunar exploration will be based on in-situ resource utilization (ISRU) techniques. The most abundant raw material on the Moon is lunar regolith, which, however, is very scarce on Earth, making the study of simulants a necessity. The objective of this study is to characterize and investigate the sintering behavior of EAC-1A lunar regolith simulant. The characterization of the simulant included the determination of the phase assemblage, characteristic temperatures determination and water content analysis. The results are discussed in the context of sintering experiments of EAC-1A simulant, which showed that the material can be sintered to a relative density close to 90%, but only within a very narrow range of temperatures (20–30 °C). Sintering experiments were performed for sieved and unsieved, as well as for dried and non-dried specimens of EAC-1A. In addition, an analysis of the densification and mechanical properties of the sintered specimens was done. The sintering experiments at different temperatures showed that the finest fraction of sieved simulant can reach a higher maximum sintering temperature, and consequently a higher densification and biaxial strength. The non-dried powder exhibited higher densification and biaxial strength after sintering compared to the dried specimen. This difference was explained with a higher green density of the non-dried powder during pressing, rather than due to an actual influence on the sintering mechanism. Nevertheless, drying the powder prior to sintering is important to avoid the overestimation of the strength of specimens to be fabricated on the Moon. KW - Lunar regolith KW - Ceramics KW - Microstructure KW - Sintering KW - Softening temperature PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-592668 SN - 2045-2322 VL - 13 SP - 1 EP - 14 PB - Springer Nature AN - OPUS4-59266 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Han, Ying A1 - Kruse, Julius A1 - Rosalie, Julian A1 - Radners, J. A1 - von Hartrott, P. A1 - Skrotzki, Birgit T1 - Influence of mean stress and overaging on fatigue life of aluminum alloy EN AW-2618A N2 - Fatigue tests were performed on the forged aluminum alloy EN AW-2618A in the T61 state. Different stress ratios (R = -1, R = 0.1) were selected to study the influence of mean stress on fatigue life. Two overaged states (10 h/230 ◦C, 1000 h/230 ◦C) were also tested to investigate the influence of overaging on fatigue life. Transmission electron microscopy (TEM) was used to characterize the precipitates (S-phase), which are mainly responsible for the strength of the alloy. A fractographic analysis was also performed to determine the failure mode. Overaging reduces the fatigue life compared to the T61 state. The longer the aging time, the lower the fatigue resistance. The reason is the decrease in (yield) strength, which correlates with the radius of the S-phase: the precipitate radius increases by a factor of approximately two for the overaged states compared to the initial state. The analysis of the fracture surfaces showed crack initiation occurs predominantly on the outer surface and is associated with the primary phases. KW - Aluminum alloys KW - Aging KW - Fatigue KW - Microstructure KW - Electron microscopy KW - S-Phase PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-583708 SN - 0921-5093 VL - 886 SP - 1 EP - 10 PB - Elsevier B.V. AN - OPUS4-58370 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stegemann, Robert A1 - Cabeza, Sandra A1 - Pelkner, Matthias A1 - Lyamkin, Viktor A1 - Pittner, Andreas A1 - Werner, Daniel A1 - Wimpory, R. A1 - Boin, M. A1 - Kreutzbruck, Marc A1 - Bruno, Giovanni T1 - Influence of the microstructure on magnetic stray fields of low-carbon steel welds N2 - This study examines the relationship between the magnetic mesostructure with the microstructure of low carbon steel tungsten inert gas welds. Optical microscopy revealed variation in the microstructure of the parent material, in the heat affected and fusion zones, correlating with distinctive changes in the local magnetic stray fields measured with high spatial resolution giant magneto resistance sensors. In the vicinity of the heat affected zone high residual stresses were found using neutron diffraction. Notably, the gradients of von Mises stress and triaxial magnetic stray field modulus follow the same tendency transverse to the weld. In contrast, micro-X-ray fluorescence characterization indicated that local changes in element composition had no independent effect on magnetic stray fields. KW - TIG-welding KW - GMR sensors KW - Magnetic stray field KW - Neutron diffraction KW - Residual stress KW - Microstructure KW - Low carbon steel PY - 2018 U6 - https://doi.org/10.1007/s10921-018-0522-0 SN - 0195-9298 SN - 1573-4862 VL - 37 IS - 3 SP - 66,1 EP - 18 PB - Springer US CY - New York AN - OPUS4-45855 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Haas, S. A1 - Manzoni, Anna Maria A1 - Holzinger, M. A1 - Glatzel, U. T1 - Influence of high melting elements on microstructure, tensile strength and creep resistance of the compositionally complex alloy Al10Co25Cr8Fe15Ni36Ti6 N2 - Due to its matrix/γ′ structure, the compositionally complex alloy (CCA) Al10Co25Cr8Fe15Ni36Ti6 has excellent properties that fulfill the requirements for a high-temperature material. This base alloy is alloyed with small amounts of high melting elements to a further improvement of its properties, which results in different shapes, fractions and sizes of the two phases γ′ and Heusler after various homogenization and annealing steps. By correlating this microstructure with time independent and dependent mechanical properties, conclusions can be drawn about the effects of the individual phases. The needle-shaped Heusler-phase leads to bad mechanical behavior if its phase fraction is too high. A fraction below 3 vol% is not critical in tensile tests, but it reduces the creep resistance compared to a purely two-phase matrix/γ′-alloy. Sharp-edged cubic γ′-particles and a coarse Heusler-phase without sharp edges in case of the base alloy with 0.5 at.% hafnium lead to the best tensile and creep properties in the high temperature range. At 750 °C, the Hf-containing alloy clearly outperforms two commercially used alloys in the targeted area of application when it comes to creep resistance. KW - High entropy alloy KW - Creep KW - Microstructure PY - 2021 U6 - https://doi.org/10.1016/j.matchemphys.2021.125163 SN - 0254-0584 VL - 274 SP - 1 EP - 10 PB - Elsevier CY - Amsterdam AN - OPUS4-53175 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ulbricht, Alexander A1 - Avila Calderon, Luis A1 - Sommer, Konstantin A1 - Mohr, Gunther A1 - Evans, Alexander A1 - Skrotzki, Birgit A1 - Bruno, Giovanni T1 - Evolution of Creep Damage of 316L Produced by Laser Powder Bed Fusion N2 - The damage mechanisms of metallic components produced by process laser powder bed fusion differ significantly from those typically observed in conventionally manufactured variants of the same alloy. This is due to the unique microstructures of additively manufactured materials. Herein, the focus is on the study of the evolution of creep damage in stainless steel 316L specimens produced by laser powder bed fusion. X-ray computed tomography is used to unravel the influence of the process-specific microstructure from the influence of the initial void distribution on creep damage mechanisms. The void distribution of two specimens tested at 600 °C and 650 °C is analyzed before a creep test, after an interruption, and after fracture. The results indicate that the formation of damage is not connected to the initial void distribution. Instead, damage accumulation at grain boundaries resulting from intergranular cracking is observed. KW - Creep KW - Computed Tomography KW - PBF-LB/M/316L KW - Laser Powder Bed Fusion KW - Microstructure KW - AISI 316L KW - Additive Manufacturing PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-574127 SP - 1 EP - 9 PB - Wiley-VCH GmbH CY - Weinheim AN - OPUS4-57412 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -