TY - CONF A1 - Kianinejad, kaveh A1 - Fedelich, Bernard A1 - Darvishi Kamachali, Reza A1 - Schriever, Sina A1 - Manzoni, Anna Maria A1 - Agudo Jacome, Leonardo A1 - Megahed, Sandra A1 - Kamrani, Sepideh A1 - Saliwan-Neumann, Romeo T1 - Experimentally informed multiscale creep modelling of additive manufactured Ni-based superalloys N2 - Excellent creep resistance at elevated temperatures, i.e. T / T_m> 0.5, due to γ-γ’ microstructure is one of the main properties of nickel-based superalloys. Due to its great importance for industrial applications, a remarkable amount of research has been devoted to understanding the underlying deformation mechanism in a wide spectrum of temperature and loading conditions. Additive manufactured (AM) nickel-based superalloys while being governed by similar γ-γ’ microstructure, exhibit AM-process specific microstructural characteristics, such as columnar grains, strong crystallographic texture (typically <001> fiber texture parallel to build direction) and compositional inhomogeneity, which in turn leads to anisotropic creep response in both stationary and tertiary phases. Despite the deep insights achieved recently on the correlation between process parameters and the resulting microstructure, the anisotropic creep behavior and corresponding deformation mechanism of these materials are insufficiently understood so far. One reason for this is the lack of capable material models that can link the microstructure to the mechanical behavior. To overcome this challenge, a multiscale microstructure-based approach has been applied by coupling crystal plasticity (CP) and polycrystal model which enables the inclusion of different deformation mechanisms and microstructural characteristics such as crystallographic texture and grain morphology. The method has been applied to experimental data for AM-manufactured INCONEL-738LC (IN738). The effect of different slip systems, texture, and morphology on creep anisotropy at 850°C has been investigated. Results suggest a strong correlation between superlattice extrinsic stacking fault (SESF) and microtwinning and observed creep anisotropy. T2 - EUROMAT 23 CY - Frankfurt a. M., Germany DA - 04.09.2023 KW - IN738LC KW - Creep anisotropy KW - Crystal plasticity PY - 2023 AN - OPUS4-58263 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rockenhäuser, Christian A1 - Ta, N. A1 - Skrotzki, Birgit A1 - Darvishi Kamachali, Reza T1 - Chemo-mechanical coupling effect during precipitation in AlLiCu systems N2 - The influence of the chemo-mechanical coupling effect during precipitation in an AlLiCu alloy is presented and discussed. T2 - Plenary meeting DFG Priority program 1713 ("Chemomechanics") CY - Bochum, Germany DA - 19.11.2019 KW - Aluminium KW - Phase-field simulation KW - Chemo-mechanical coupling KW - Transmission electron microscopy PY - 2019 AN - OPUS4-49807 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Beygi Nasrabadi, Hossein A1 - Skrotzki, Birgit T1 - Digital representation of materials testing data for semantic web analytics: Tensile stress relaxation testing use case N2 - This study aims to represent an approach for transferring the materials testing datasets to the digital schema that meets the prerequisites of the semantic web. As a use case, the tensile stress relaxation testing method was evaluated and the testing datasets for several copper alloys were prepared. The tensile stress relaxation testing ontology (TSRTO) was modeled following the test standard requirements and by utilizing the appropriate upper-level ontologies. Eventually, mapping the testing datasets into the knowledge graph and converting the data-mapped graphs to the machine-readable Resource Description Framework (RDF) schema led to the preparation of the digital version of testing data which can be efficiently queried on the web. T2 - ICMDA 2024: 7th International Conference on Materials Design and Applications CY - Tokyo, Japan  DA - 09.04.2024 KW - Digitalization KW - Tensile stress relaxation KW - Ontology KW - Mechanical testing KW - Semantic web PY - 2024 AN - OPUS4-59979 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Feng, Wen A1 - Gemming, Thomas A1 - Giebeler, Lars A1 - Qu, Jiang A1 - Weinel, Kristina A1 - Agudo Jácome, Leonardo A1 - Büchner, Bernd A1 - González-Martínez, Ignacio T1 - Influence of magnetic field on electron beam-induced Coulomb explosion of gold microparticles in transmission electron microscopy N2 - In this work we instigated the fragmentation of Au microparticles supported on a thin amorphous carbon film by irradiating them with a gradually convergent electron beam inside the Transmission Electron Microscope. This phenomenon has been generically labeled as “electron beam-induced fragmentation” or EBIF and its physical origin remains contested. On the one hand, EBIF has been primarily characterized as a consequence of beam-induced heating. On the other, EBIF has been attributed to beam-induced charging eventually leading to Coulomb explosion. To test the feasibility of the charging framework for EBIF, we instigated the fragmentation of Au particles under two different experimental conditions. First, with the magnetic objective lens of the microscope operating at full capacity, i.e. background magnetic field B = 2 T, and with the magnetic objective lens switched off (Lorenz mode), i.e. B = 0 T. We observe that the presence or absence of the magnetic field noticeably affects the critical current density at which EBIF occurs. This strongly suggests that magnetic field effects play a crucial role in instigating EBIF on the microparticles. The dependence of the value of the critical current density on the absence or presence of an ambient magnetic field cannot be accounted for by the beam-induced heating model. Consequently, this work presents robust experimental evidence suggesting that Coulomb explosion driven by electrostatic charging is the root cause of EBIF. KW - Electron beam-induced fragmentation KW - Coulomb explosion KW - X-ray diffraction KW - Lorenz transmission electron microscopy PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-600247 DO - https://doi.org/10.1016/j.ultramic.2024.113978 SN - 0304-3991 VL - 262 SP - 1 EP - 8 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-60024 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Darvishi Kamachali, Reza A1 - Rockenhäuser, Christian A1 - Saxena, A. A1 - Skrotzki, Birgit A1 - Umer Bilal, M. A1 - Ramirez, Daniela Valencia A1 - Schwarze, C. A1 - Häusler, I. T1 - Chemo-mechanical Coupling Effect During Precipitation in AlLi and AlLiCu systems N2 - The chemo-mechanical coupling effect during precipitation in AlLi and AlLiCu systems is presented and effects of chemo-mechanical coupling on materials with different microstructures is discussed. The results of the simulations are then compared to electron-microscopical investigations. T2 - Plenary meeting DFG Priority program 1713 ("Chemomechanics") CY - Bochum, Germany DA - 17.12.2018 KW - Al-Li alloys KW - Phase field simulation KW - Precipitation KW - Inverse ostwald ripening KW - Transmission electron microscopy PY - 2018 AN - OPUS4-46961 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rockenhäuser, Christian A1 - Häusler, Ines A1 - Darvishi Kamachali, Reza A1 - Heidl, Daniel A1 - Skrotzki, Birgit T1 - Influence of heat treatment and creep loading on an Al-Cu-Li alloy N2 - The influence of heat treatment and creep loading on the microstructure of an Al-Cu-Li alloy was investigated. Especially the formation of different precipitates (T1 and Theta') were characterized and the microstructural changes under different ageing conditions (with and without external strain) were investigated to determine the effect od stress on the ageing process. T2 - 19th International Microscopy Congress (IMC19) CY - Sydney, Australia DA - 09.09.2018 KW - Aluminium KW - Degradation KW - Coarsening KW - Dark-field transmission electron microscopy PY - 2018 AN - OPUS4-46129 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rockenhäuser, Christian A1 - Häusler, Ines A1 - Darvishi Kamachali, Reza A1 - Heidl, Daniel A1 - Skrotzki, Birgit T1 - Influence of heat treatment and creep loading on an Al-Cu-Li alloy N2 - The influence of heat treatment and creep loading on the microstructure of an Al-Cu-Li alloy was investigated. Especially the formation of different precipitates (T1 and Theta') were characterized and the microstructural changes under different ageing conditions (with and without external strain) were investigated to determine the effect od stress on the ageing process. T2 - 19th International Microscopy Congress (IMC19) CY - Sydney, Australia DA - 09.09.2018 KW - Aluminium KW - Degradation KW - Coarsening KW - Dark-field transmission electron microscopy PY - 2018 AN - OPUS4-46131 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wang, Lei A1 - Darvishi Kamachali, Reza T1 - Density-based Thermodynamics of Microstructure Defects N2 - Systematic microstructure design requires reliable thermodynamic descriptions and phase diagrams of each and all microstructure elements. While such descriptions are well established for most bulk phases, thermodynamic assessment of crystal defects is greatly challenged by their individualistic aspects. In this talk, we present a density-based thermodynamic concept to describe defects based on available bulk thermodynamic data. Here dealing with grain boundaries (GBs), we apply this concept to compute GB (phase) diagram. Applications to segregation engineering of GBs in bulk and nanocrystalline alloys will be presented. We further develop this model to include the effect of elastic interactions due to atom size mismatch and obtain the corresponding GB (phase) diagram for the ternary Al-Cu-Li system. T2 - TMS 2021 CY - Online meeting DA - 15.03.2021 KW - Microstrucrue Design KW - Density-based Thermodynamics PY - 2021 AN - OPUS4-52337 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Darvishi Kamachali, Reza A1 - Wang, Lei A1 - Lin, L. L. A1 - Manzoni, Anna Maria A1 - Skrotzki, Birgit A1 - Thompson, G. B. T1 - CALPHAD-informed density-based grain boundary thermodynamics N2 - The Gibbs free energy of a grain boundary is a complex thermodynamic function of temperature, pressure, and composition. These complexities add to the intrinsic crystallographic and chemical constraints imposed by the adjacent bulk phase. Recently we have proposed a density-based model for assessing grain boundary thermodynamics that enables a CALPHAD-informed description of the grain boundary. As such, the Gibbs free energy of the grain boundary is directly linked with available CALPHAD thermodynamic data. In this talk, new aspects of interfacial segregation and phase transformation are revealed by benchmarking the current model for various experimental cases, including several steels, high-entropy alloys and aluminum alloys. The effects of elastic interactions on the grain boundary segregation and the application of the model to a nanocrystalline Pt-Au alloy, with numerous grain boundaries of various characters, will be discussed. T2 - DPG (Deutsche Physiker Gesellschaft) CY - Online meeting DA - 27.09.2021 KW - Density-based model KW - Defects thermodynamics KW - Defects phase diagram KW - CALPHAD KW - Crystal Defects PY - 2021 AN - OPUS4-53556 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Darvishi Kamachali, Reza T1 - Interfacial Spinodals N2 - Despite their finite spatial extent, interfaces can have profound impacts on microstructure properties. This is because of their distinct phase-like properties distinguishing them from the adjacent homogeneous bulk structure. When noticed by solute atoms, interfaces can experience their own chemical phase changes. In this talk, we investigate the constrained states of chemically decomposed phases at interfaces. A density-based theory of interfaces is proposed to describe the confined chemical decomposition at general grain boundaries. Here the grain boundary is viewed as a lesser dense, defected structure with reference to the corresponding bulk structure. Using this picture, the thermodynamic origins of interfacial spinodal phenomena are revealed. We also show that transient interfacial spinodals can be activated over a large alloy composition range, enabling kinetic engineering of interfacial chemistry. T2 - TMS 2021 CY - Online meeting DA - 15.03.2021 KW - Microstrucrue Design KW - Spinodal Decomposition KW - Interfacial Spinodal PY - 2021 AN - OPUS4-52338 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -