Dokument-ID Dokumenttyp Autoren/innen Persönliche Herausgeber/innen Haupttitel Abstract Auflage Verlagsort Verlag Herausgeber (Institution) Erscheinungsjahr Titel des übergeordneten Werkes Jahrgang/Band ISBN Veranstaltung Veranstaltungsort Beginndatum der Veranstaltung Enddatum der Veranstaltung Ausgabe/Heft Erste Seite Letzte Seite URN DOI Lizenz Datum der Freischaltung OPUS4-57412 Zeitschriftenartikel Ulbricht, Alexander; Avila Calderon, Luis; Sommer, Konstantin; Mohr, Gunther; Evans, Alexander; Skrotzki, Birgit; Bruno, Giovanni Evolution of Creep Damage of 316L Produced by Laser Powder Bed Fusion 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. Weinheim Wiley-VCH GmbH 2023 Advanced Engineering Materials 1 9 urn:nbn:de:kobv:b43-574127 10.1002/adem.202201581 https://creativecommons.org/licenses/by/4.0/deed.de 2023-05-04 OPUS4-57452 Zeitschriftenartikel Zocca, Andrea; Müller, Bernd R.; Laquai, René; Kupsch, Andreas; Wieder, Frank; Benemann, Sigrid; Wilbig, Janka; Günster, Jens; Bruno, Giovanni Microstructural characterization of AP40 apatite-wollastonite glass-ceramic 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. Amsterdam Elsevier Science 2023 Ceramics international 49 8 12672 12679 10.1016/j.ceramint.2022.12.130 2023-05-12 OPUS4-58370 Zeitschriftenartikel Han, Ying; Kruse, Julius; Rosalie, Julian; Radners, J.; von Hartrott, P.; Skrotzki, Birgit Influence of mean stress and overaging on fatigue life of aluminum alloy EN AW-2618A 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. Elsevier B.V. 2023 Materials Science & Engineering A 886 1 10 urn:nbn:de:kobv:b43-583708 10.1016/j.msea.2023.145660 https://creativecommons.org/licenses/by/4.0/deed.de 2023-09-21 OPUS4-59266 Zeitschriftenartikel Ginés-Palomares, J.-C.; Fateri, M.; Schubert, T.; de Peindray d'Ambelle, L.; Simon, Sebastian; Gluth, Gregor; Günster, Jens; Zocca, Andrea Material aspects of sintering of EAC-1A lunar regolith simulant 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. Springer Nature 2023 Scientific Reports 13 1 14 urn:nbn:de:kobv:b43-592668 10.1038/s41598-023-50391-y https://creativecommons.org/licenses/by/4.0/deed.de 2024-01-02 OPUS4-54226 Zeitschriftenartikel Ávila Calderón, Luis Alexander; Graf, B.; Rehmer, Birgit; Petrat, T.; Skrotzki, Birgit; Rethmeier, Michael Characterization of Ti-6Al-4V fabricated by multilayer laser powder-based directed energy deposition 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. Weinheim Wiley-VCH 2022 Advanced engineering materials 1 15 urn:nbn:de:kobv:b43-542262 10.1002/adem.202101333 https://creativecommons.org/licenses/by/4.0/deed.de 2022-01-19 OPUS4-54305 Zeitschriftenartikel Kingsbery, Phillip; Stephan-Scherb, Christiane Effect of KCl deposits in high-temperature corrosion on chromium-rich steels in SO2-containing atmosphere 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. Weinheim Wiley-VCH 2022 Materials and corrosion 73 5 758 770 urn:nbn:de:kobv:b43-543056 10.1002/maco.202112901 https://creativecommons.org/licenses/by/4.0/deed.de 2022-02-11 OPUS4-54590 Zeitschriftenartikel Suárez Ocano, Patricia; Fries, S. G.; Lopez-Galilea, I.; Darvishi Kamachali, Reza; Roik, J.; Agudo Jácome, Leonardo The AlMo0.5NbTa0.5TiZr refractory high entropy superalloy: Experimental findings and comparison with calculations using the CALPHAD method 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. Amsterdam Elsevier 2022 Materials and design 217 1 13 urn:nbn:de:kobv:b43-545906 10.1016/j.matdes.2022.110593 https://creativecommons.org/licenses/by-nc-nd/4.0/deed.de 2022-04-04 OPUS4-56467 Zeitschriftenartikel Rodrigues, A. C. P.; Feller, A.; Agudo Jácome, Leonardo; Azevedo, C. R. F. Use of synthetic Fe3O4-rich tribofilms to investigate the effect of microconstituents, temperature and atmosphere on the friction coefficient during pin-on-disc tribotest 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. IOP Pobilishing 2022 Surface Topography: Metrology and Properties 10 4 044009-1 044009-18 10.1088/2051-672X/ac9d51 2022-12-07 OPUS4-53175 Zeitschriftenartikel Haas, S.; Manzoni, Anna Maria; Holzinger, M.; Glatzel, U. Influence of high melting elements on microstructure, tensile strength and creep resistance of the compositionally complex alloy Al10Co25Cr8Fe15Ni36Ti6 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. Amsterdam Elsevier 2021 Materials chemistry and physics 274 1 10 10.1016/j.matchemphys.2021.125163 2021-09-03 OPUS4-51989 Zeitschriftenartikel Rockenhäuser, Christian; Rowolt, C.; Milkereit, B.; Darvishi Kamachali, Reza; Kessler, O.; Skrotzki, Birgit On the long-term aging of S-phase in aluminum alloy 2618A 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. Springer Nature 2021 Journal of Materials Science 56 14 8704 8716 urn:nbn:de:kobv:b43-519899 10.1007/s10853-020-05740-x https://creativecommons.org/licenses/by/4.0/deed.de 2021-01-13