TY - CONF A1 - Ávila Calderón, Luis Alexander A1 - Rehmer, Birgit A1 - Schriever, Sina A1 - Ulbricht, Alexander A1 - Agudo Jácome, Leonardo A1 - Sommer, Konstantin A1 - Mohr, Gunther A1 - Skrotzki, Birgit T1 - Creep and fracture behavior of conventionally and additively manufactured stainless steel 316L N2 - A critical task within the frame of establishing process-structure-property-performance relationships in additive manufacturing (AM) of metals is producing reliable and well-documented material behavior’s data and knowledge regarding the structure-property correlation, including the role of defects. After all, it represents the basis for developing more targeted process optimizations and more reliable predictions of performance in the future. Within this context, this contribution aims to close the actual gap of limited historical data and knowledge concerning the creep behavior of the widely used austenitic stainless steel 316L, manufactured by Laser-Powder-Bed-Fusion (L-PBF). To address this objective, specimens from conventional hot-rolled and AM material were tested under application-relevant conditions according to existing standards for conventional material, and microstructurally characterized before and after failure. The test specimens were machined from single blocks from the AM material. The blocks were manufactured using a standard scan and build-up strategy and were subsequently heat-treated. The creep behavior is described and comparatively assessed based on the creep lifetime and selected creep curves and characteristic values. The effect of defects and microstructure on the material’s behavior is analyzed based on destructive and non-destructive evaluations on selected specimens. The AM material shows shorter creep lives, reaches the secondary creep stage much faster and at a lower strain, and features lower creep ductility compared to its conventional counterpart. The creep damage behavior of the AM material is more microstructure than defect controlled and is characterized by the formation and accumulation of single intergranular damage along the whole volume. Critical features identified are the grain morphology and the grain-boundary as well as the dislocation’s density. Micro-computed tomography (µCT) proves to be an alternative to metallography to analyze the creep damage. T2 - ASTM International Conference on Additive Manufacturing 2020 CY - Online meeting DA - 16.11.2020 KW - 316L KW - Creep behavior KW - Laser powder bed fusion KW - Additive manufacturing KW - Microstructure PY - 2020 AN - OPUS4-51823 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mieller, Björn A1 - Schulz, Bärbel A1 - Rabe, Torsten T1 - Tailoring the spring constant of ceramic helical compression springs N2 - Ceramic springs combine attractive properties for applications in machinery, metrology, and sensor technology. They are electrically insulating, non-magnetic, provide a linear stress-strain behavior, and are stable at high temperatures and in corrosive environments. Generally, the precise dimensioning of a ceramic spring with respect to the spring constant is challenging. Different models are described, but many of these calculations do not match the actual spring properties. We demonstrate a reliable approach for the dimensioning and manufacturing of helical compression springs with a rectangular winding cross-section. Based on the German standard DIN 2090, which is referring to metallic springs, the spring constant can be calculated based on shear modulus, diameter, height, widths, and number of windings. Different ceramic springs were produced by milling of sintered hollow cylinders of zirconia, alumina and silicon nitride. The experimental spring constants are in very good agreement with the calculated values. Spring constants of zirconia springs were varied over three orders of magnitude between 0.02 N/mm and 5 N/mm by purposeful adaption of the spring geometry. The combination of dimensioning based on DIN 2090 and precise hard machining offers a reliable technology for the fabrication of tailored ceramic springs for special applications. T2 - 45th International Conference and Exhibition on Advanced Ceramics and Composites (ICACC 2021) CY - Online meeting DA - 08.02.2021 KW - Ceramics KW - Hard machining KW - Spring constant PY - 2021 AN - OPUS4-52136 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cornelsen Sampaio Kling, I. A1 - Pauw, Brian Richard A1 - Agudo Jácome, Leonardo A1 - Archanjo, B. S. A1 - Simão, R. A. T1 - Development and characterization of starch film and the incorporation of silver nanoparticles N2 - Starch is one of the biopolymers being used for bioplastic synthesis. For production, starch can be combined with different plasticizers, starches from different plant sources and even with nanomaterials to improve or to add film properties. The challenge of adding these, e.g. in the form of silver nanoparticles (AgNp) is to determine the concentration so as to avoid impairing the properties of the film, agglomeration or altering the visual characteristics of the film. In this study, a starch film synthesis route and the incorporation of silver nanoparticles has been proposed in order not to alter the properties of the film while maintaining the transparency and a clear colour of the starch film. The results showed that the proposed synthesis route is promising, efficient, reproducible, fast and the film has good mechanical properties. T2 - Semana MetalMat & Painal PEMM 2020 CY - Online meeting DA - 23.11.2020 KW - Biofilm KW - Silver nanoparticle KW - Starch KW - Starch nanoparticle PY - 2020 SP - 1 EP - 2 AN - OPUS4-51940 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Suárez Ocano, Patricia A1 - Gadelmeier, C. A1 - Gratzel, U. A1 - Agudo Jácome, Leonardo T1 - High temperature and low stress creep behavior of the refractory chemically complex alloy AlMo 0.5 NbTa 0.5 TiZr N2 - The refractory chemically complex alloy (rCCA) AlMo0.5NbTa0.5TiZr, with a density of 7.4 g/cm3, shows a compressive ultimate strength of 772 MPa at 1000 °C, comparatively surpassing Ni-base and other rCCAs. Its dual-phase microstructure, with a high volume fraction (≈ 62%) of cuboidal and plate-like particles coherently embedded in a continuous matrix, resembles the well-known pattern of the γ/γ" in Ni-base superalloys. Its developers have thus implied that it could stand as structural alloy for high temperature (HT) applications. Here, we report the HT creep properties and the underlying microstructural changes of the rCCA AlMo0.5NbTa0.5TiZr to propose deformation and degradation micromecanisms for this regime. The material was produced by arc-melting and subsequently heat treated in argon: at 1400 °C for 24 h plus a hot isostatic pressure treatment at 1370 °C and 170 MPa for 4 h, with a cooling rate of 10 K/min. Miniaturized tensile specimens (≈ 28 x 7 x 2 mm) were cut and polished to a quality of 1 μm. Creep tests were conducted in vacuum in the respective temperature and stress range 800-1200 °C and 30-120 MPa. For observation, thin slices were extracted from the gauge length, away from the fracture surface, grinded to a thickness of 100 μm, and electropolished to electron transparency. The microstructure was observed on the electropolished specimens using scanning (S) as well as transmission (T) electron microscopy (EM). The Norton plot gives Norton exponents of about 3.1 and 3.2 for temperatures of 1000 and 1100 °C, respectively. Curiously, creep rate minima are very close for a stress level of 30. The starting microstructure reflects a macroscopically lean coarse grain structure and a microscopically fine-meshed basketweave structure with coherency dislocations only around coarsened particles usually close to subgrain boundaries. Results are discussed on the base of variations of this starting microstructure after interrupted and ruptured creep tests. T2 - 15th International Conference on Creep and Fracture of Engineering Materials and Structures CY - Online meeting DA - 14.06.2021 KW - Creep behavior KW - Chemically complex alloy KW - Cow stress PY - 2021 AN - OPUS4-53388 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Suárez Ocano, Patricia A1 - Fries, S. G. A1 - Lopez-Galilea, I. A1 - Ruttert, B. A1 - Theissen, W. A1 - Agudo Jácome, Leonardo T1 - Effect of the heat treatment in the microstructure of a refractory chemically complex alloy N2 - A set of some unexpected and interesting microstructures has put the so-called complex concentrated alloys (CCAs) in the eye of the scientific community. The AlMo0.5NbTa0.5TiZr refractory (r)CCA, aimed at substituting Ni-base superalloys in gas turbine applications, belongs to this alloy family. After a two-stage heat treatment, this rCCA morphologically resembles the typical a two-phase microstructure of the latter. The objective of this work consists in determining the effect of the two stages of the heat treatment on the microstructure of the AlMo0.5NbTa0.5TiZr alloy to eventually improve it in terms of homogeneity and porosity. T2 - Third International Conference on High Entropy Materials (2020) CY - Berlin, Germany DA - 27.09.2020 KW - Annealing KW - Hot isostatic pressing KW - Refractory chemically complex alloy KW - Microstructure PY - 2020 AN - OPUS4-53386 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 Jácome, 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 - Wehmann, N. A1 - Lenting, C. A1 - Stawski, Tomasz A1 - Agudo Jácome, Leonardo A1 - Jahn, S. T1 - Non classical nucleation in calcium sulfates Insights from the hyper arid Atacama Desert N2 - Gypsum (CaSO4∙2H2O) and anhydrite (CaSO4) are among the dominant evaporite minerals in the Atacama Desert [1]. They are distributed ubiquitously, and play a key role in local landscape evolution. The formation mechanism of especially anhydrite has been a matter of scientific debate for more than a century [2]. To date, there exists no model that can reliably predict anhydrite formation at earth’s surface conditions. While thermodynamics favor its formation [3], it is hardly achieved on laboratory time scales at conditions fitting the Atacama Desert. Long induction times for nucleation have recently been modeled by Ossorio et al. [4]. However, anhydrite can be readily found in the Atacama Desert. Recently, the mineral was synthesized in flow-through reactors as a byproduct of K-jarosite dissolution at high water activity (aw=0.98) and room temperature [5], even-though the thermodynamic stability field begins only under a value of ~0.8. Additionally, recent studies investigated the nano-structure of various calcium-sulfates, which advocate for highly non-classical crystallization behavior [6]. The specific roles of particulates, ionic or organic reagents working as catalysts for the non-classical crystallization pathway remain to be determined. Here, we present recent results from flow-through experiments as well as analyses of anhydrite samples from the Atacama Desert. Flow-through experiments were performed to systematically explore the domains of flow rate, composition, ionic-strengths and starting materials. Neither primary, nor secondary anhydrite was produced in any of these experiments. Analyses on Atacama samples reveal the existence of at least three distinct anhydrite facies, with differing mineralogy and micro- to nano-structures. The facies are (1) aeolian deposits with sub-µm grain sizes, (2) (sub-)surface nodules that formed from aeolian deposits and (3) selenites with secondary anhydrite rims. Possible mechanisms of their formation will be discussed. T2 - Goldschmidt2023 CY - Lyon, France DA - 13.07.2023 KW - Gypsum KW - Anhydrite KW - Atacama Desert KW - Local landscape evolution PY - 2023 AN - OPUS4-58988 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Winckelmann, Alexander A1 - Hoffmann, V. A1 - Morcillo, Dalia A1 - Agudo Jácome, Leonardo A1 - Leonhardt, Robert A1 - Richter, Silke A1 - Recknagel, Sebastian A1 - Abad Andrade, Carlos Enrique A1 - You, Zengchao T1 - Chemical characterization of aging processes in high energy-density lithium-ion batteries N2 - Introduction Lithium-ion batteries (LIBs) are one key technology to overcome the climate crisis and energy transition challenges. Demands of electric vehicles on higher capacity and power drives research on innovative cathode and anode materials. These high energy-density LIBs are operated at higher voltages, leading to increased electrolyte decay and the current collectors' degradation. Even though this fundamental corrosion process significantly affects battery performance, insufficient research is being done on the aluminum current collector. Fast and convenient analytical methods are needed for monitoring the aging processes in LIBs. Methods In this work glow-discharge optical emission spectrometry (GD-OES) was used for depth profile analysis of aged cathode material. The measurements were performed in pulsed radio frequency mode. Under soft and controlled plasma conditions, high-resolution local determination (in depth) of the elemental composition is possible. Scanning electron microscopy (SEM) combined with a focused ion beam (FIB) cutting and energy dispersive X-ray spectroscopy (EDX) was used to confirm GD-OES results and obtain additional information on elemental distribution. Results The aging of coin cells manufactured with different cathode materials (LCO, LMO, NMC111, NMC424, NMC532, NMC622, and NMC811) was studied. GD-OES depth profiling of new and aged cathode materials was performed. Quantitative analysis was possible through calibration with synthetic standards and correction by sputter rate. Different amounts of aluminum deposit on the cathode surface were found for different materials. The deposit has its origin in the corrosion of the aluminum current collector. The results are compatible with results from FIB-EDX. However, GD-OES is a faster and less laborious analytical method. Therefore, it will accelerate research on corrosion processes in high energy-density batteries. Innovative aspects - Quantitative depth profiling of cathode material -Monitoring of corrosion processes in high energy-density lithium-ion batteries - Systematic investigation of the influence of different cathode materials T2 - ANAKON 2023 CY - Vienna, Austria DA - 11.04.2023 KW - Lithium Ion Batteries KW - GD-OES KW - Depth-profiling PY - 2023 AN - OPUS4-58586 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wehmann, N. A1 - Lenting, C. A1 - Stawski, T. M. A1 - Agudo Jácome, Leonardo T1 - Anhydrite formation in planetary surface environments - The case of the Atacama Desert N2 - Gypsum (CaSO4∙2H2O), bassanite (CaSO4∙0.5H2O), and anhydrite (CaSO4) are essential evaporite minerals for the evolution of hyper-arid surface environments on Earth and Mars (Voigt et al. 2019; Vaniman et al. 2018). The formation mechanism of especially anhydrite has been a matter of scientific debate for more than a century (van’t Hoff et al. 1903). To date, there exists no model that can reliably predict anhydrite formation at earth’s surface conditions. While thermodynamics favor its formation, it is hardly achieved on laboratory time scales at conditions fitting either the Atacama Desert on Earth, or the surface of Mars (Wehmann et al. 2023). In light of most recent developments (e.g. Stawski et al. 2016), that advocate for a complex, non-classical nucleation mechanism for all calcium sulphates, we present an analysis of natural samples from the Atacama Desert to identify key features that promote the nucleation and growth of anhydrite under planetary surface conditions. Our analyses reveal at least three distinct anhydrite facies, with differing mineralogy and micro- to nano-structures. The facies are (1) aeolian deposits with sub-μm grain sizes, (2) (sub-)surface nodules that formed from aeolian deposits and (3) selenites with secondary anhydrite rims. Possible mechanisms of their formation will be discussed. T2 - 10th Granada-Münster Discussion Meeting CY - Münster, Germany DA - 29.11.2023 KW - Calcium sulfates KW - Nucleation KW - Planetary surface KW - Hyper-arid PY - 2023 AN - OPUS4-59111 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Weinel, Kristina A1 - Gonzalez-Martinez, I. A1 - Agudo Jácome, Leonardo T1 - Damage induced by electric field of microparticles in the electron microscope N2 - Damage induced by electric field (DIEF) that happens in the transmission electron microscope (TEM) when converging the electron beam (e-beam) on microparticles (MPs) can be used to synthesis new nanomaterial and nanomaterial compositions. The research questions are to clarify the limits and possibilities of the method regarding materials that can be produced, systems to which it is applicable and working beam parameters. Synthesis of nano-objects from microparticles using DIEF in TEM could be shown for different materials. Additionally, DIEF using the e-beam in a scanning electron microscope (SEM) can also be used to synthesis nano-objects. A deeper material analysis of this nano-objects was done using TEM and shows that the material of the nanoparticles (NPs) can be gold or/and silicon. Furthermore, the size of the NPs depends on the distance to the center of DIEF whereby the larger NPs are closer to the center. The areas of gold NPs are promising candidates for plasmonic or photonic devices for energy storage or transport. T2 - PhD-Day 2022 CY - Berlin, Germany DA - 06.09.2022 KW - Electron microscopy KW - Electron beam induced modification KW - Gold nanoparticles PY - 2022 AN - OPUS4-58264 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -