TY - JOUR A1 - Ulbricht, Alexander A1 - Ávila Calderón, 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 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-574127 DO - https://doi.org/10.1002/adem.202201581 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 - TY - JOUR A1 - Schilling, Markus A1 - Bayerlein, Bernd A1 - von Hartrott, Philipp A1 - Waitelonis, Jörg A1 - Birkholz, Henk A1 - Portella, Pedro Dolabella A1 - Skrotzki, Birgit T1 - FAIR and Structured Data: A Domain Ontology Aligned with Standard‐Compliant Tensile Testing N2 - The digitalization of materials science and engineering (MSE) is currently leading to remarkable advancements in materials research, design, and optimization, fueled by computer‐driven simulations, artificial intelligence, and machine learning. While these developments promise to accelerate materials innovation, challenges in quality assurance, data interoperability, and data management have to be addressed. In response, the adoption of semantic web technologies has emerged as a powerful solution in MSE. Ontologies provide structured and machine‐actionable knowledge representations that enable data integration, harmonization, and improved research collaboration. This study focuses on the tensile test ontology (TTO), which semantically represents the mechanical tensile test method and is developed within the project Plattform MaterialDigital (PMD) in connection with the PMD Core Ontology. Based on ISO 6892‐1, the test standard‐compliant TTO offers a structured vocabulary for tensile test data, ensuring data interoperability, transparency, and reproducibility. By categorizing measurement data and metadata, it facilitates comprehensive data analysis, interpretation, and systematic search in databases. The path from developing an ontology in accordance with an associated test standard, converting selected tensile test data into the interoperable resource description framework format, up to connecting the ontology and data is presented. Such a semantic connection using a data mapping procedure leads to an enhanced ability of querying. The TTO provides a valuable resource for materials researchers and engineers, promoting data and metadata standardization and sharing. Its usage ensures the generation of finable, accessible, interoperable, and reusable data while maintaining both human and machine actionability. KW - Data Interoperability KW - Domain Ontology Development KW - FAIR Data Management KW - Knowledge Representation KW - Tensile Test Ontology KW - Semantic Web Technologies PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-598142 DO - https://doi.org/10.1002/adem.202400138 SN - 1438-1656 SP - 1 EP - 19 PB - Wiley VHC-Verlag AN - OPUS4-59814 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bhadeliya, Ashok A1 - Rehmer, Birgit A1 - Fedelich, Bernard A1 - Jokisch, T. A1 - Skrotzki, Birgit A1 - Olbricht, Jürgen T1 - Fatigue and fracture in dual-material specimens of nickel-based alloys fabricated by hybrid additive manufacturing N2 - The integration of additive manufacturing with traditional processes, termed hybrid additive manufacturing, has expanded its application domain, particularly in the repair of gas turbine blade tips. However, process-related defects in additively manufactured materials, interface formation, and material property mismatches in dual-material structures can significantly impact the fatigue performance of components. This investigation examines the low cycle fatigue and fatigue crack growth behaviors in dual-material specimens of nickel-based alloys, specifically the additively manufactured STAL15 and the cast alloy 247DS, at elevated temperatures. Low cycle fatigue experiments were conducted at temperatures of 950 °C and 1000 °C under a range of strain levels (0.3%–0.8%) and fatigue crack growth tests were conducted at 950 °C with stress ratios of 0.1 and −1. Fractographic and microscopic analyses were performed to comprehend fatigue crack initiation and crack growth mechanisms in the dual-material structure. The results consistently indicated crack initiation and fatigue fracture in the additively manufactured STAL15 material. Notably, fatigue crack growth retardation was observed near the interface when the crack extended from the additively manufactured STAL15 material to the perpendicularly positioned interface. This study highlights the importance of considering yield strength mismatch, as well as the potential effects of residual stresses and grain structure differences, in the interpretation of fatigue crack growth behavior at the interface. KW - Hybrid additive manufacturing KW - Dual-material nickel-based alloys KW - High-temperature fatigue crack growth KW - Low cycle fatigue PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-609340 DO - https://doi.org/10.1016/j.jmrt.2024.08.211 SN - 2238-7854 VL - 32 SP - 3737 EP - 3749 PB - Elsevier B.V. AN - OPUS4-60934 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Beygi Nasrabadi, Hossein A1 - Norouzi, Ebrahim A1 - Sack, Harald A1 - Skrotzki, Birgit T1 - Performance Evaluation of Upper‐Level Ontologies in Developing Materials Science Ontologies and Knowledge Graphs N2 - This study tackles a significant challenge in ontology development for materials science: selecting the most appropriate upper‐level ontologies for creating application‐level ontologies and knowledge graphs. Focusing on the use case of Brinell hardness testing, the research assesses the performance of various top‐level ontologies (TLOs)—basic formal ontology (BFO), elementary multiperspective material ontology (EMMO), and provenance ontology (PROVO)—in developing Brinell testing ontologies (BTOs). Consequently, three versions of BTOs are created using combinations of these TLOs along with their integrated mid‐ and domain‐level ontologies. The performance of these ontologies is evaluated based on ten parameters: semantic richness, domain coverage, extensibility, complexity, mapping efficiency, query efficiency, integration with other ontologies, adaptability to different data contexts, community acceptance, and documentation and maintainability. The results show that all candidate TLOs can effectively develop BTOs, each with its distinct advantages. BFO provides a well‐structured, understandable hierarchy, and excellent query efficiency, making it suitable for integration across various ontologies and applications. PROVO demonstrates balanced performance with strong integration capabilities. Meanwhile, EMMO offers high semantic richness and domain coverage, though its complex structure impacts query efficiency and integration with other ontologies. KW - Materials Science KW - Ontology KW - Knowledge Graph PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-612227 DO - https://doi.org/10.1002/adem.202401534 SN - 1527-2648 SP - 1 EP - 18 PB - Wiley AN - OPUS4-61222 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sonntag, Nadja A1 - Piesker, Benjamin A1 - Ávila Calderón, Luis A1 - Mohr, Gunther A1 - Rehmer, Birgit A1 - Agudo Jácome, Leonardo A1 - Hilgenberg, Kai A1 - Evans, Alexander A1 - Skrotzki, Birgit T1 - Tensile and Low‐Cycle Fatigue Behavior of Laser Powder Bed Fused Inconel 718 at Room and High Temperature N2 - This study investigates the room‐ and high‐temperature (650 °C) tensile and low‐cycle‐fatigue behavior of Inconel 718 produced by laser powder bed fusion (PBF‐LB/M) with a four‐step heat treatment and compares the results to the conventional wrought material. The microstructure after heat treatment is characterized on different length scales. Compared to the wrought variant, the elastic and yield properties are comparable at both test temperatures while tensile strength, ductility, and strain hardening capacity are lower. The fatigue life of the PBF‐LB/M variant at room temperature is slightly lower than that of the wrought material, while at 650 °C, it is vice versa. The cyclic stress response for both material variants is characterized by cyclic softening, which is more pronounced at the higher test temperature. High strain amplitudes (≥0.7%) at room temperature and especially a high testing temperature result in the formation of multiple secondary cracks at the transitions of regions comprising predominantly elongated grain morphology and columns of stacked grains with ripple patterns in the PBF‐LB/M material. This observation and pronounced crack branching and deflection indicate that the cracks are controlled by sharp micromechanical gradients and local crystallite clusters. KW - Additive manufacturing KW - Fatigue damage KW - Heat treatment KW - Inconel 718 KW - Laser powder bed fusion KW - Low-cycle fatigue KW - Tensile strength PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-599316 DO - https://doi.org/10.1002/adem.202302122 SN - 1527-2648 SP - 1 EP - 17 PB - Wiley AN - OPUS4-59931 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bhadeliya, Ashok A1 - Rehmer, Birgit A1 - Fedelich, Bernard A1 - Jokisch, T. A1 - Skrotzki, Birgit A1 - Olbricht, Jürgen T1 - Fatigue crack growth behavior of Alloy 247DS brazed joints at high temperatures N2 - Gas turbine components made of nickel-based alloys can be repaired through diffusion brazing. However, process-induced imperfections, defects within the brazing zone, and material property mismatches between the braze alloy and base material may facilitate crack initiation and propagation, ultimately leading to early component failure. To gain insight into the crack growth mechanism and quantitatively characterize fatigue crack growth behavior within brazing zones, fatigue crack growth (FCG) experiments were conducted on brazed joint specimens of nickel-based alloy Alloy 247DS at a temperature of 950 ◦C and a stress ratio R = 0.1. The FCG tests were complemented by fractographic and microstructural analyses, to elucidate the relationship between crack growth mechanisms and the microstructure of the brazed joint. The results demonstrate stable crack propagation within the brazing zone and the nickel-based braze alloy. The latter contains brittle eutectic boride phases and intermetallic phases that reduce the resistance to crack propagation compared to the parent material. This study demonstrates the applicability of standard FCG experimental procedures to fusion zones, thereby enabling a preliminary understanding of crack growth behavior in brazing zones. KW - Diffusion brazing KW - High-temperature fatigue crack growth KW - Nickel-based alloys KW - Alloy 247DS PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-615250 DO - https://doi.org/10.1016/j.msea.2024.147488 SN - 0921-5093 VL - 918 SP - 1 EP - 15 PB - Elsevier B.V. AN - OPUS4-61525 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Beygi Nasrabadi, Hossein A1 - Hanke, Thomas A1 - Skrotzki, Birgit T1 - Semantic Representation of Low‐Cycle‐Fatigue Testing Data Using a Fatigue Test Ontology and ckan.kupferdigital Data Management System N2 - Addressing a strategy for publishing open and digital research data, this article presents the approach for streamlining and automating the process of storage and conversion of research data to those of semantically queryable data on the web. As the use case for demonstrating and evaluating the digitalization process, the primary datasets from low‐cycle‐fatigue testing of several copper alloys are prepared. The fatigue test ontology (FTO) and ckan.kupferdigital data management system are developed as two main prerequisites of the data digitalization process. FTO has been modeled according to the content of the fatigue testing standard and by reusing the basic formal ontology, industrial ontology foundry core ontology, and material science and engineering ontology. The ckan.kupferdigital data management system is also constructed in such a way that enables the users to prepare the protocols for mapping the datasets into the knowledge graph and automatically convert all the primary datasets to those machine‐readable data which are represented by the web ontology language. The retrievability of the converted digital data is also evaluated by querying the example competency questions, confirming that ckan.kupferdigital enables publishing open data that can be highly reused in the semantic web. KW - Accessible KW - CKAN KW - Interoperable KW - Digitalizations KW - Ontologies KW - Reusable data KW - Fatigue testing PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-604991 UR - https://onlinelibrary.wiley.com/doi/10.1002/adem.202400675 DO - https://doi.org/10.1002/adem.202400675 SN - 1527-2648 SP - 1 EP - 11 PB - Wiley AN - OPUS4-60499 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Singh, Shobhit Pratap A1 - Löwe, Peter A1 - Schriever, Sina A1 - Olbricht, Jürgen A1 - Rehmer, Birgit A1 - Nolze, Gert A1 - Skrotzki, Birgit T1 - High-throughput creep evaluation of IN738LC in bending using digital image correlation at 850 °C N2 - High-temperature alloys, when used in structural applications, undergo slow time-dependent deformation known as creep. Assessing creep behavior is critical for estimating the in-service life of these alloys. Conventionally, uniaxial creep tests are widely conducted at elevated temperatures to determine creep rates. In recent years, bending creep of cantilevers, when combined with digital image correlation (DIC), has emerged as a promising high-throughput technique for rapidly estimating creep life. However, the applicability of bending creep above 700 ◦C for high-temperature alloys using DIC has not been fully established. In this work, we compare uniaxial creep rates of the nickel-based superalloy IN738LC with bending creep rates measured at 850 ◦C using high-temperature DIC. The bending creep data show excellent agreement with uniaxial creep results in the stress range of 240–360 MPa. The measured creep xponent, a critical rate-determining parameter, is found to be ~8 for both uniaxial and bending creep, with the rate data scattered within a factor of two. An in-house experimental setup was developed to perform bending creep tests at high temperatures, with strain monitored through DIC. Our results demonstrate that bending creep, combined with DIC, provides a reliable and efficient method for creep testing of high-temperature alloys. Compared to conventional uniaxial creep experiments, this approach requires significantly less time and material, thereby reducing effort, energy, and cost. We anticipate that this technique will serve as a foundation for testing precious high-temperature materials. For instance, in ongoing rapid discoveries of advanced alloys, in-service creep life can be evaluated much faster with reduced material requirements. Moreover, this method holds strong potential for application to high-entropy alloys and additively manufactured alloys designed for demanding high-temperature environments. KW - Digital image correlation KW - Bending creep KW - Nickel-based superalloys KW - High throughput testing KW - High-temperature materials PY - 2025 UR - https://www.sciencedirect.com/science/article/pii/S0921509325017034?via%3Dihub DO - https://doi.org/10.1016/j.msea.2025.149479 VL - 950 SP - 1 EP - 12 PB - Elsevier B.V. AN - OPUS4-64814 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Beygi Nasrabadi, Hossein A1 - Klotz, Ulrich E. A1 - Tiberto, Dario A1 - Vafaeenezhad, Hossein A1 - Mishurova, Tatiana A1 - Skrotzki, Birgit T1 - Effect of keyhole and lack-of-fusion pores on the anisotropic microstructure and mechanical properties of PBF-LB/M-produced CuCrZr alloy N2 - Due to the high reflectance and heat conductivity of copper and its alloys, the processing window for laser-based powder bed fusion (PBF-LB/M) processing of high-density copper components fundamentally overlaps with conduction and keyhole melting zones, resulting in the emergence of certain pores in the structure of printed parts. The present research aims to study how the development of process-induced lack-of-fusion or keyhole porosities during the PBF-LB/M process can affect the anisotropic microstructure and mechanical properties of the produced copper alloys. For this purpose, several samples were produced utilizing a similar CuCrZr-feedstock composition but varied process parameters from different areas of the PBF-LB/M processing window, specifically at laser powers of 300 W and 380 W which define the boarders of the conduction and keyhole regimes. X-ray computed tomography (XCT) revealed that the 300-W and 380-W samples achieved relative densities of 98.88% and 99.99%, respectively, with elongated lack-of-fusion pores forming at 300 W and semi-spherical keyhole pores at 380 W. Microstructural analyses employing scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) demonstrated strong anisotropy in different build directions of the samples, owing to the growth of long columnar grains with intense < 101  orientation along the build directions. Here, the emergence of different types of pores can cause competition between the epitaxial growth of columnar grains and the heterogeneous nucleation of new grains on the layers’ interfaces, thereby significantly varying the grain size, preferred orientation, crystallographic texture, and microstructural anisotropy of the samples. Furthermore, compression tests and nanoindentation measurements of the printed alloys in the longitudinal and transverse directions revealed that the 300 W and 380 W samples exhibited compressive strength anisotropies of 0.061 and 0.072, and average nanoindentation hardness values of 1.3 GPa and 1.5 GPa, respectively. The orientation of elongated lack-of-fusion porosities perpendicular to the loading axis was identified as the most damaging factor, significantly reducing mechanical performance compared to the uniformly distributed keyhole pores. KW - Copper Alloy KW - Laser-based powder bed fusion KW - Microstructure KW - Mechanical properties KW - X-ray computed tomography (XCT) KW - Porosity KW - Anisotropy PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625655 DO - https://doi.org/10.1007/s40964-025-00972-2 SN - 2363-9520 SP - 1 EP - 15 PB - Springer Science and Business Media LLC AN - OPUS4-62565 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ávila Calderón, Luis A1 - Rehmer, Birgit A1 - Schriever, Sina A1 - Ulbricht, Alexander A1 - Agudo Jácome, Leonardo A1 - Sommer, Konstantin A1 - Mohr, Gunther A1 - Skrotzki, Birgit A1 - Evans, Alexander T1 - Creep and creep damage behavior of stainless steel 316L manufactured by laser powder bed fusion N2 - This study presents a thorough characterization of the creep properties of austenitic stainless steel 316L produced by laser powder bed fusion (LPBF 316L) contributing to the sparse available data to date. Experimental results (mechanical tests, microscopy, X-ray computed tomography) concerning the creep deformation and damage mechanisms are presented and discussed. The tested LPBF material exhibits a low defect population, which allows for the isolation and improved understanding of the effect of other typical aspects of an LPBF microstructure on the creep behavior. As a benchmark to assess the material properties of the LPBF 316L, a conventionally manufactured variant of 316L was also tested. To characterize the creep properties, hot tensile tests and constant force creep tests at 600 °C and 650 °C are performed. The creep stress exponents of the LPBF material are smaller than that of the conventional variant. The primary and secondary creep stages and the times to rupture of the LPBF material are shorter than the hot rolled 316L. Overall the creep damage is more extensive in the LPBF material. The creep damage of the LPBF material is overall mainly intergranular. It is presumably caused and accelerated by both the appearance of precipitates at the grain boundaries and the unfavorable orientation of the grain boundaries. Neither the melt pool boundaries nor entrapped gas pores show a significant influence on the creep damage mechanism. KW - 316L KW - Laser Powder Bed Fusion (LPBF) KW - Creep behavior KW - Additive Manufacturing KW - AGIL PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-539373 DO - https://doi.org/10.1016/j.msea.2021.142223 SN - 0921-5093 VL - 830 SP - 142223 PB - Elsevier B.V. AN - OPUS4-53937 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -