@misc{JedynakSviridovBambachetal., author = {Jedynak, Angelika and Sviridov, Alexander and Bambach, Markus and Beckers, Daniel and Graf, Gregor}, title = {On the Potential of Using Selective Laser Melting for the Fast Development of Forging Alloys at the Example of Waspaloy}, series = {Procedia Manufacturing; Part of Special issue: 23rd International Conference on Material Forming}, volume = {47}, journal = {Procedia Manufacturing; Part of Special issue: 23rd International Conference on Material Forming}, editor = {Bambach, Markus}, issn = {2351-9789}, doi = {10.1016/j.promfg.2020.04.138}, pages = {1149 -- 1153}, language = {en} } @misc{HirtlerJedynakSydowetal., author = {Hirtler, Markus and Jedynak, Angelika and Sydow, Benjamin and Sviridov, Alexander and Bambach, Markus}, title = {A Study On The Mechanical Properties Of Hybrid Parts Manufactured By Forging And Wire Arc Additive Manufacturing}, series = {Procedia Manufacturing; Part of Special issue: 23rd International Conference on Material Forming}, volume = {47}, journal = {Procedia Manufacturing; Part of Special issue: 23rd International Conference on Material Forming}, editor = {Bambach, Markus}, issn = {2351-9789}, doi = {10.1016/j.promfg.2020.04.136}, pages = {1141 -- 1148}, language = {en} } @misc{SefidiIsrarBuhletal., author = {Sefidi, Moein Pakdel and Israr, Rameez and Buhl, Johannes and Bambach, Markus}, title = {Rule-Based Path Identification for Direct Energy Deposition}, series = {Procedia Manufacturing; Part of Special issue: 23rd International Conference on Material Forming}, volume = {47}, journal = {Procedia Manufacturing; Part of Special issue: 23rd International Conference on Material Forming}, editor = {Bambach, Markus}, issn = {2351-9789}, doi = {10.1016/jpromfg.2020.04.133}, pages = {1134 -- 1140}, language = {en} } @misc{BlumbergLiBesongetal., author = {Blumberg, Julian and Li, Zhoulong and Besong, Lemopi Isidore and Polte, Mitchel and Buhl, Johannes and Uhlmann, Eckart and Bambach, Markus}, title = {Deformation error compensation of industrial robots in single point incremental forming by means of data-driven stiffness model}, series = {26th International Conference on Automation and Computing (ICAC), 2-4 Sept. 2021, Portsmouth, United Kingdom}, journal = {26th International Conference on Automation and Computing (ICAC), 2-4 Sept. 2021, Portsmouth, United Kingdom}, isbn = {978-1-86043-557-7}, doi = {10.23919/ICAC50006.2021.9594138}, pages = {6}, language = {en} } @misc{BuhlKloeppelMertenetal., author = {Buhl, Johannes and Kl{\"o}ppel, Thomas and Merten, Mathias and Haufe, Andre and Israr, Rameez and Bambach, Markus}, title = {Numerical prediction of process-dependent properties of high-performance Ti6Al4 in LS-DYNA}, series = {ESAFORM 2021 : 24th International Conference on Material Forming}, journal = {ESAFORM 2021 : 24th International Conference on Material Forming}, doi = {doi: 10.25518/esaform21.1496}, language = {en} } @misc{HaaseWernerKraeuseletal., author = {Haase, R. and Werner, M. and Kr{\"a}usel, V. and Alimov, Artem and Sviridov, Alexander and H{\"a}rtel, Sebastian}, title = {Improved formability of HMGF components by preforming in an upset bulging process}, series = {IOP Conference Series}, volume = {1238}, journal = {IOP Conference Series}, publisher = {IOP Publishing Ltd.}, address = {Bristol}, doi = {10.1088/1757-899X/1238/1/012018}, pages = {8}, language = {en} } @misc{ColditzHaertelDrehmann, author = {Colditz, Pascal and H{\"a}rtel, Sebastian and Drehmann, Rico}, title = {Numerical and Experimental Modeling of an Inline Forming Process for the Mechanical Property Optimization of Cold Gas Sprayed Material Composites}, series = {Production at the Leading Edge of Technology : Proceedings of the 11th Congress of the German Academic Association for Production Technology (WGP), Dresden, September 2021}, journal = {Production at the Leading Edge of Technology : Proceedings of the 11th Congress of the German Academic Association for Production Technology (WGP), Dresden, September 2021}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-78423-2}, issn = {2194-0533}, doi = {10.1007/978-3-030-78424-9_41}, pages = {366 -- 374}, language = {en} } @misc{HartRawungBuhlHaerteletal., author = {Hart-Rawung, Thawin and Buhl, Johannes and H{\"a}rtel, Sebastian and Bambach, Markus}, title = {Intelligent Iterative Experimental Design to Achieve Maximum Model Quality for Phase Change of 22MnB5}, series = {Key Engineering Materials}, volume = {926}, journal = {Key Engineering Materials}, publisher = {Verlag Trans Tech Publications Ltd}, doi = {https://doi.org/10.4028/p-0cnty5}, pages = {2031 -- 2039}, language = {en} } @misc{ErtugrulAlimovSviridovetal., author = {Ertugrul, G{\"o}khan and Alimov, Artem and Sviridov, Alexander and H{\"a}rtel, Sebastian}, title = {Machine learning application for optimization of laser directed energy deposition process for aerospace component rapid prototyping in additive manufacturing}, series = {Materials Research Proceedings}, volume = {41}, journal = {Materials Research Proceedings}, publisher = {Taylor\&Francis}, issn = {2474-395X}, doi = {10.21741/9781644903131-31}, pages = {271 -- 282}, abstract = {Abstract. The paper proposes a methodology for determining the optimal L-DED parameters based on the minimum number planned of L-DED trials. A dataset compiled from planned L-DED experiments was used to train a machine learning model. The algorithm demonstrated a robust ability to predict the output metrics with notable accuracy and proposed a theoretical framework that modeled the complex relationships between the input variables and the resulting critical welding properties for AM. The application of the developed model and its comparison with conventional methods thus offers a methodical approach to determining the optimum process parameters in advance. This is a step towards the development and production of additively manufactured components for future digital twin application in the aerospace industry.}, language = {en} } @misc{JenschEissingRichardetal., author = {Jensch, Felix and Eissing, Katharina and Richard, Williams and Trautmann, Marcus and Yang, Yitong and Dubinin, Sergej and H{\"a}rtel, Sebastian}, title = {Improving the structural integrity of challenging to manufacture LPBF components with toolpath correction}, series = {Materials Research Proceedings}, volume = {41}, journal = {Materials Research Proceedings}, publisher = {Materials Research Forum LLC}, issn = {2474-395X}, doi = {10.21741/9781644903131-12}, pages = {110 -- 119}, abstract = {This work deals with the influence of optimised exposure strategies on the distortion and microstructure of components susceptible to overheating and warpage. Therefore, different distortion-prone specimen geometries of 316L were fabricated with the standard parameters, as well as with exposure strategies optimised by machine learning, which were generated using the AMAIZE software package. The manufactured samples were analysed with regard to distortion. The results of the distortion analysis were then linked with the results of the digital tomography from AMAIZE. Furthermore, components were manufactured that tend to overheat due to their geometry and orientation on the substrate plate. The influence of overheating during the LPBF process on the microstructure and porosity was investigated along the build-up direction by means of an EBSD analysis and a porosity analysis. With the presented approach for optimising the exposure strategy with AMAIZE, it could be shown that a successful production of distortion- prone components with a porosity of less than 1 \% is possible in the first trial.}, language = {en} } @misc{ApelHaertelSzyndler, author = {Apel, Markus and H{\"a}rtel, Sebastian and Szyndler, Joanna}, title = {Prediction of the microstructure morphology after the WAAM process based on the FEM simulation results}, series = {Materials Research Proceedings}, volume = {41}, journal = {Materials Research Proceedings}, doi = {10.21741/9781644903131-3}, pages = {22 -- 31}, abstract = {To improve understanding of the material behavior of additive-produced components, this paper focuses on the development of a numerical model that reproduces a Wire Arc Additive Manufacturing (WAAM) process, with particular attention given to the evolution of the microstructure. In this study, a finite element model in Simufact Welding software is developed, that replicates a real wire arc welding process of building a multilayer straight wall. Microscopy analysis of the weld wall cut in the middle of its length gave information about the expected microstructure morphology at different levels of the build wall. The whole experimental setup is reproduced in the software Simufact Welding. Simulation results in the form of temperature-time and temperature gradient-time history are then used as superimposed thermal conditions to simulate the microstructure evolution at different areas of the welded part by using MICRESS software.}, language = {en} } @misc{HaertelSzyndlerPakdelSefidietal., author = {H{\"a}rtel, Sebastian and Szyndler, Joanna and Pakdel Sefidi, Moein and J{\"a}ger, Reyk}, title = {Prediction of the evolution of material properties during the AM process based on the FEM simulation and experimental results}, series = {Materials Research Proceedings}, volume = {41}, journal = {Materials Research Proceedings}, doi = {10.21741/9781644903131-5}, pages = {40 -- 49}, abstract = {To deepen the understanding of material behavior after additive manufacturing, this article focuses on the prediction of material properties after the Wire Arc Additive Manufacturing (WAAM) process. Particular attention is put on the temperature curves in the various phases of the welding process, which influence the final material properties, especially the hardness of the resulting part. A total of nine components in the form of walls were produced using the WAAM process, with the number of layers varying from 1 to 9. By experimentally analyzing the welded parts, which were cut in the middle of their length, it was possible to gain insights into the development of hardness at selected points. The entire test setup was simulated in the Simufact Welding FE-software. The simulation results in the form of temperature-time diagrams were then correlated with the real hardness measurements at the corresponding points. In this way, a model was developed that for the first time considers the development of hardness as a result of cooling after the welding process as well as the change in hardness as a result of reheating due to the application of additional layers.}, language = {en} } @misc{JenschBuhlLaueetal., author = {Jensch, Felix and Buhl, Johannes and Laue, Robert and H{\"a}rtel, Sebastian}, title = {Application of the plane-strain-compression-test to determine the local mechanical properties of LPBF-manufactured 316l components}, series = {Material Forming: The 26th International ESAFORM Conference on Material Forming, Krak{\´o}w, Poland, April 19-21, 2023}, volume = {28}, journal = {Material Forming: The 26th International ESAFORM Conference on Material Forming, Krak{\´o}w, Poland, April 19-21, 2023}, doi = {10.21741/9781644902479-17}, pages = {149 -- 149}, language = {en} } @misc{JedynakErtugrulNeumannetal., author = {Jedynak, Angelika and Ertugrul, G{\"o}khan and Neumann, Andreas and Pippig, Robert and H{\"a}rtel, Sebastian}, title = {Semi-finished powder of aluminum matrix composite for a direct energy deposition additive manufacturing}, series = {Material Forming: The 26th International ESAFORM Conference on Material Forming, Krak{\´o}w, Poland, April 19-21, 2023}, volume = {28}, journal = {Material Forming: The 26th International ESAFORM Conference on Material Forming, Krak{\´o}w, Poland, April 19-21, 2023}, doi = {10.21741/9781644902479-22}, pages = {199 -- 206}, language = {en} } @misc{SzyndlerSchmidtHaertel, author = {Szyndler, Joanna and Schmidt, Alexander and H{\"a}rtel, Sebastian}, title = {Determination of welding heat source parameters for fem simulation based on temperature history and real bead shape}, series = {Material Forming : The 26th International ESAFORM Conference on Material Forming, Krak{\´o}w, Poland, April 19-21, 2023}, journal = {Material Forming : The 26th International ESAFORM Conference on Material Forming, Krak{\´o}w, Poland, April 19-21, 2023}, edition = {28}, doi = {10.21741/9781644902479-18}, pages = {159 -- 168}, language = {en} } @misc{SydowHaertel, author = {Sydow, Benjamin and H{\"a}rtel, Sebastian}, title = {Temperature Control During the Process Combination Welding and Rolling for Enabling Full Recrystallization with Homogenized Grain Size Distribution}, series = {Proceedings of the 14th International Conference on the Technology of Plasticity : current trends in the technology of plasticity, ICTP 2023, volume 1}, journal = {Proceedings of the 14th International Conference on the Technology of Plasticity : current trends in the technology of plasticity, ICTP 2023, volume 1}, editor = {Mocellin, Katia and Bouchard, Pierre-Olivier and Bigot, R{\´e}gis and Balan, Tudor}, publisher = {Springer}, address = {Cham}, isbn = {978-3-031-41022-2}, doi = {10.1007/978-3-031-41023-9_20}, pages = {192 -- 202}, abstract = {Welding with an electric arc is mainly used as a joining technology, where a high energy input is required locally for the joining process. Due to the heat input, the welded bead is characterized by a heat affected zone, that consists of an inhomogeneous microstructure of different phases and grain sizes. This leads to non-optimal mechanical properties. One way to improve the microstructure is to induce plastic deformation (e.g. by rolling), which can enable recrystallization mechanisms, that homogenize the microstructure and therefore can optimize the material properties. Yet, the recrystallization mechanisms require a minimum temperature to be activated. On one hand, the in-situ heat input during welding can be used for this in a process combination of welding and rolling but might not be enough, to reach or hold this recrystallization temperature during rolling. An excessive heat input on the other hand leads to too high temperatures, causing significant grain growth, that also negatively affect the mechanical properties. In any case, a certain temperature range over time has to be maintained. The temperature can be controlled by burners for pre-heating and post-heating, and the heating power can be controlled separately. In this numerical study, burner heat models are used to simulate the temperature-controlled process combination of welding one single bead with a subsequent rolling step for the mild steel St37/S235JR. The influence of the pre- and post-heating could be numerically proven and suitable heating combinations were found, that allow a full recrystallization with a nearly homogenous grain size distribution.}, language = {en} } @misc{JaegerSydowSchmidtetal., author = {J{\"a}ger, Reyk and Sydow, Benjamin and Schmidt, Alexander and Witt, Susanne and H{\"a}rtel, Sebastian}, title = {Design and Manufacturing of a Lightweight Press-Hardening Forming Tool by Wire Arc Additive Manufacturing}, series = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, Volume 3}, journal = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, Volume 3}, editor = {Mocellin, Katia}, publisher = {Springer}, isbn = {978-3-031-41340-7}, issn = {2195-4364}, doi = {10.1007/978-3-031-41341-4_25}, pages = {235 -- 246}, abstract = {Press-hardening is an important metal sheet manufacturing process to improve the metal sheet properties during forming with an inline quenching process. This requires higher cooling rates often obtained by cooling channels within the tools, that enable the formation of martensite for a high strength. The manufacturing of those forming tools with internal cooling channels is quite complex, time and material consuming and therefore expensive. Optimal cooling channel geometry cannot be realized by conventional machining operations, that limits cooling efficiency too. Wire Arc Additive Manufacturing (WAAM) is a layer-wise welding process, that allows the manufacturing of near net shapes and internal cooling channels. In contrast to conventional machining, manufacturing of a complex lightweight design forming tool can be realized by WAAM. This will further reduce the WAAM process time and material consumption. However, the lightweight design reduces on one hand the thermal mass and thus the capability of heat transfer, making cooling via the cooling channels more crucial. On the other hand, elastic tool deformation has to be as low as possible. In this study, a press-hardening forming tool made of S235JR is designed and manufactured by means of WAAM. FEM analysis are performed to optimize the design of the forming tool regarding lightweight aspects. Simple near net shapes of cooling channels are considered for a simplification of the WAAM process. The forming tool is mechanically tested to compare and evaluate the stiffness with the FEM analysis.}, language = {en} } @misc{NeumannHaertel, author = {Neumann, Andreas and H{\"a}rtel, Sebastian}, title = {Limitations of a new forming process for vault structured recuperator tubes}, series = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity ICTP 2023 - Volume 1}, journal = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity ICTP 2023 - Volume 1}, editor = {Mocellin, Katia}, edition = {1}, publisher = {Springer Nature}, address = {Cham, Schweiz}, isbn = {978-3-031-41022-2}, issn = {2195-4356}, doi = {10.1007/978-3-031-41023-9_58}, pages = {577 -- 583}, abstract = {Classic forming technologies can make a difference to a climate-neutral economy. This also applies to the production of innovative hydrogen coolers (recuperators). To improve the efficiency of hydrogen coolers, heat transfer and heat flux can be increased by tube structures made by pressing spherical elements on their surface. Hydrogen is passed through the tubes of the recuperators and the cooling medium flows across it (Figure 1a). The tube serves as an atmosphere separator. Structured tubes can increase the power den-sity with the same dimensions. Figure 1b shows a process for introducing the structure into the pipe using radially and symmetrically arranged tools. Sheet metal forming usually involves pressing with structural tools, bending into a tube, and longitudinally welding. However, producing small tube diameters in the range of one inch presents a technical challenge. The challenge considered in this paper is to develop a new structuring process while maintaining the structural integrity and wall thickness of the tubes. This study aims to determine the feasibility of a multi-stage vault structuring process for recuperator tubes us-ing heat-resistant semi-finished products.}, language = {en} } @misc{JhanjiSydowAdamsetal., author = {Jhanji, Avantika and Sydow, Benjamin and Adams, Tom-Eric and Habisch, Stefan and H{\"a}rtel, Sebastian}, title = {Influence of the Initial Microstructure on the Mechanical Behavior During Forming for Inline Manufacturing Process Routes}, series = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 2}, journal = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 2}, publisher = {Springer Nature Switzerland}, address = {Cham}, isbn = {978-3-031-40919-6}, issn = {2195-4356}, doi = {10.1007/978-3-031-40920-2_53}, pages = {513 -- 524}, abstract = {With a view of sustainability and the rising energy costs currently, manufacturing processes of metals are becoming increasingly focused on optimizing process parameters such as energy and time consumption. A conventional hot-forming process route currently involves casting an ingot, letting it cool down, and heating it up again for the hot-forming process (see Fig. 1a). In order to implement the combination of casting and forging, avoiding the reheating cycle and using less energy, by utilizing the casting heat (see Fig. 1b), a methodology was developed within the present work to quantify the influence of the resulting microstructure as a function of the cooling rate on the forming and recrystallization behavior (see Fig. 1c). For this purpose, AISI 301 austenitic stainless-steel cast samples with different cast cooling rates were generated. An in-situ high-temperature microscope is used to determine the holding time and the heating rate. Dilatometer tests are performed to characterize the interaction between initial microstructure and the flow curves to verify the determination method (see Fig. 1d). The aim was to demonstrate whether the microstructure evolution and mechanical behavior is affected by the initial microstructure. The flow curves and the post-forming microstructure show a higher degree of recrystallization in fast-cooled microstructure than slow-cooled microstructure. Hence, it was found that the initial microstructure and the associated temperature history does have an impact on the mechanical properties.}, language = {en} } @misc{GrafPippigLehnertetal., author = {Graf, Marcel and Pippig, Robert and Lehnert, Tim and Jedynak, Angelika and H{\"a}rtel, Sebastian}, title = {Aluminium-Matrix-Composites (AMC) for Hot Forged Components}, series = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 1}, journal = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 1}, editor = {Mocellin, Katia}, publisher = {Springer Nature Switzerland}, address = {Cham}, isbn = {978-3-031-41022-2}, issn = {2195-4356}, doi = {10.1007/978-3-031-41023-9_4}, pages = {36 -- 47}, abstract = {The development of new materials or material systems is always accompanied by the development of processing technologies suitable for the material. The reduction of process steps, the saving of material and the optimization of material properties are aims of forming processes. The basis for this is the comprehensive characterisation of the thermos-physical and thermos-mechanical technologically relevant material behaviour, taking into account the real process conditions. In the present work, the material-specific process limits were determined by means of experimental simulation and used in the numerical simulation in order, on the one hand, to identify the forming steps for optimizing the manufacturing conditions and, on the other hand, to be able to set the final material properties. It was essential to homogenize the casting microstructure for the forming processes and to adjust it to globulitical grains by solution annealing. The previously limited forming behaviour of the cast AlSi9Mg alloy with 20 vol.-\% SiC could be increased thus to forging-relevant plastic strains without occurring damages. Based on the comprehensive temperature-dependent material data, a one-step and resource-efficient manufacturing process for AMC materials by hot forming could be developed with the help of the FE software Simufact Forming and validated in reality under near-industrial conditions.}, language = {en} } @misc{BuhlHaertelBesong, author = {Buhl, Johannes and H{\"a}rtel, Sebastian and Besong, Lemopi Isidore}, title = {Temperature Control of the Two-Point Incremental Forming Process to Achieve Homogeneous Martensite Content Based on Finite Element Simulations}, series = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 1}, journal = {Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 1}, editor = {Mocellin, Katia}, publisher = {Springer}, address = {Cham}, isbn = {978-3-031-41022-2}, issn = {2195-4356}, doi = {10.1007/978-3-031-41023-9_74}, pages = {739 -- 747}, abstract = {Deformation-induced martensite has been observed in the incremental sheet forming of metastable austenitic stainless steels (MASS). The presence of martensite improves the characteristics of the springs. Martensite transformation usually occurs at low temperatures (<70 ℃). Depending on the tool speed, incremental forming of disk springs requires between 3 to 5 min. The forming time needs to be short to increase the process output in industrial settings. However, accelerating the process leads to high temperatures above the martensite transformation temperature that suppress martensite formation, necessitating temperature control during forming. It is suggested to enhance the martensite content of the blank by cooling during the forming operation. In this contribution, two-point incremental sheet forming is conducted to determine the influence of process temperature on the phase content of MASS disk springs. A temperature-dependent phase change material model that includes the strain rate effect is implemented in finite element (FE) simulations to predict the martensite content. FE simulations are performed to investigate the convection coefficients and cooling time leading to process temperatures below 70 ℃. The framework can be used to control and speed up the incremental forming of disk springs while maintaining a high martensite content.}, language = {en} } @misc{GruegerSzyndlerJenschetal., author = {Gr{\"u}ger, Lennart and Szyndler, Joanna and Jensch, Felix and H{\"a}rtel, Sebastian}, title = {Porosity analysis of L-PBF manufactured AZ91D components}, series = {Materials research proceedings}, volume = {54}, journal = {Materials research proceedings}, publisher = {Materials Research Forum LLC}, address = {Millersville, PA}, isbn = {978-1-64490-359-9}, issn = {2474-395X}, doi = {10.21741/9781644903599-22}, pages = {199 -- 208}, abstract = {Several materials for joint replacement parts approved in medical technology are being investigated. Magnesium alloys are very suitable for implants due to the similar strength properties between magnesium alloys and human bone. Therefore, the present work aims to examine the parameters for producing the magnesium alloy AZ91D. For this purpose, 16 samples were manufactured with varying laser power and exposure speed and examined using µCT analyses. As a result, densities between 99.56 and 95.21 percent were achieved. The samples with the lowest density were subjected to a HIP process to increase the relative density. However, a further µCT analysis revealed only minor positive effects of the HIP process. An analysis of the number and size of the pores indicates that the pores bonded together instead of being closed.}, language = {en} } @misc{SviridovAlimovJenschetal., author = {Sviridov, Alexander and Alimov, Artem and Jensch, Felix and Dubinin, Sergej and H{\"a}rtel, Sebastian}, title = {Influence of surface quality on performance of forging dies produced by additive manufacturing the role of post-processing in LPBF-manufactured X55 steel}, series = {Materials research proceedings}, volume = {54}, journal = {Materials research proceedings}, publisher = {Materials Research Forum LLC}, address = {Millersville, PA}, isbn = {978-1-64490-359-9}, issn = {2474-395X}, doi = {10.21741/9781644903599-27}, pages = {245 -- 253}, abstract = {Laser Powder Bed Fusion (LPBF) has become a key technology in additive manufacturing (AM), enabling the production of highly complex geometries and is increasingly applied in serial production. With the continuous expansion of processable materials, LPBF is now also being considered for the manufacturing of forging dies. However, LPBF application for tool steels such as H11 is limited by their susceptibility to hot cracking. Maraging steels like X55 present a promising alternative due to their superior resistance to such defects. A major advantage of this technology for forging dies lies in the potential elimination of extensive machining required to refine rough as-built surfaces, thereby streamlining and accelerating the production process. Achieving this goal requires systematic investigations into non-machining post-processing techniques for targeted surface modifications, along with a comprehensive evaluation of mechanical properties and surface integrity after post-processing. This study examines the influence of different post-processing methods on the surface quality, mechanical properties, and tribological behavior of LPBF-manufactured X55 (1.2709) specimens. To evaluate surface roughness and mechanical performance, slope specimens and tensile specimens were analyzed in different conditions: as-built, mechanically machined, sandblasted, and treated via Hirtisition®. Additionally, flat dies were produced and subjected to ring compression tests to determine friction factors under varying surface and lubrication conditions. The findings emphasize the crucial role of post-processing in optimizing the surface quality and functional performance of LPBF-manufactured forging tools, offering valuable insights for their further development.}, language = {en} } @misc{OkoloEissingWilliamsetal., author = {Okolo, Chukwuemeka and Eissing, Katharina and Williams, Richard and Jensch, Felix and Fergani, Omar and H{\"a}rtel, Sebastian}, title = {Investigation of the influence of AI-controlled process parameter adjustment on the mechanical properties of LBPF-manufactured parts}, series = {Materials research proceedings}, volume = {54}, journal = {Materials research proceedings}, publisher = {Materials Research Forum LLC}, address = {Millersville, PA}, isbn = {978-1-64490-359-9}, issn = {2474-395X}, doi = {10.21741/9781644903599-24}, pages = {218 -- 227}, abstract = {This study investigates the influence of machine learning (ML) based process parameter adjustments on the microstructure, relative density, and mechanical properties of laser powder bed fusion (LPBF)-manufactured components, focusing on AlSi10Mg and Ti6Al4V. The ML algorithm optimizes the thermal history by adjusting laser power and exposure time at the vector level, ensuring consistent cooling and solidification dynamics. Microscopy revealed a refined and homogeneous microstructure in the optimized AlSi10Mg samples, with reduced grain size (4.92 µm compared to 6.37 µm in non-optimized samples). Relative density analysis showed a significant improvement for optimized samples, achieving consistent values across top, middle, and bottom sections of the specimen. Hardness measurements confirmed the homogenized mechanical properties, with more uniform and elevated hardness values observed in optimized samples. This study demonstrates that ML-based process optimization minimizes defects like porosity and microcracks, enabling improved mechanical performance and efficient process qualification for LPBF-manufactured parts. The findings underline the potential of AI-driven solutions for addressing complex geometrical and thermal challenges in LPBF process.}, language = {en} } @misc{EmdadiJenschSzyndleretal., author = {Emdadi, Aliakbar and Jensch, Felix and Szyndler, Joanna and Huang, Hsuan-Po and H{\"a}rtel, Sebastian and Weiß, Sabine}, title = {Void closure behavior during hot forming of an Fe-Al alloy}, series = {Materials research proceedings}, volume = {54}, journal = {Materials research proceedings}, publisher = {IWA Publishing}, address = {Millersville, PA}, isbn = {978-1-64490-359-9}, issn = {2474-395X}, doi = {10.21741/9781644903599-99}, pages = {927 -- 935}, abstract = {Hot forging is a forming process that can be used as a post-processing treatment to close residual porosity and refine the microstructure of additively manufactured materials, resulting in improved mechanical properties. During hot forging, void closure occurs through plastic deformation resulting from a predominantly compressive stress state at elevated temperatures. In the present work, Fe-25Al-1.5Ta (at. \%) samples have been produced by laser powder bed fusion (LPBF) using a larger layer thickness and scan speed than commonly used to achieve a target porosity fraction of approximately 10\%. Full densification is attempted in the subsequent hot compression step at various height reduction ratios. The as-built LPBF samples contained 8-10\% voids. After deformation to true strains of 0.2, 0.4, and 0.6, the void fraction decreased significantly to approximately 4\%, 2.3\%, and 1.1\%, respectively. Hot compression resulted in the complete closure of large pores with a size range of 200-300 µm and a significant reduction in the size of small to medium pores. These results show potential for improving the productivity of the LPBF by speeding up the process by increasing layer thickness and scanning speed while maintaining a reasonable density. Full densification should be achieved by subsequent hot forging.}, language = {en} } @misc{ErtugrulEmdadiHaertel, author = {Ertugrul, G{\"o}khan and Emdadi, Aliakbar and H{\"a}rtel, Sebastian}, title = {Advancements in iron aluminide alloy processing : a comparative study with DED alternatives}, series = {Materials research proceedings}, volume = {54}, journal = {Materials research proceedings}, publisher = {Materials Research Forum LLC}, address = {Millersville, PA}, issn = {2474-395X}, doi = {10.21741/9781644903599-28}, pages = {254 -- 263}, abstract = {This article investigates the processing and characterization of iron aluminide lightweight alloy by plasma ultrasonic atomization and laser powder based directed energy deposition (DED-LB/p) and its comparison with other additive manufacturing alternatives. DED-LB/p provides precisely controllable process parameters, a wide range of feed materials supplied in powder form, a relatively high deposition rate and low heat input. These features favor the DED - LB/p process for novel materials such as iron aluminide. Thanks to a combination of desirable properties such as low density, high specific strength, low material cost, excellent oxidation resistance, and corrosion resistance, Fe-Al has established considerable potential to replace high-alloy chromium steels and, in some cases, even superalloys in high-temperature applications. In this study, Fe-Al alloy was first atomized into powder form from a commercial rod with core of aluminum and sleeve of a commercial low alloy-steel by plasma ultrasonic atomization. The resulting powder was then used for additive manufacturing with DED-LB/p in order to reduce cost and analyze the process chain. The results show that the use of powder produced by plasma ultrasonic atomization from commercial raw materials in the DED-LB/p process provides an effective combination for additive manufacturing of Fe-Al alloy and has some advantages over the alternative WAAM method.}, language = {en} }