TY - GEN A1 - Neumann, Andreas A1 - Härtel, Sebastian ED - Mocellin, Katia T1 - Limitations of a new forming process for vault structured recuperator tubes T2 - Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity ICTP 2023 - Volume 1 N2 - 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. KW - Forming limit, model-based evaluation, Tool Development Y1 - 2023 SN - 978-3-031-41022-2 U6 - https://doi.org/10.1007/978-3-031-41023-9_58 SN - 2195-4356 SP - 577 EP - 583 PB - Springer Nature CY - Cham, Schweiz ET - 1 ER - TY - GEN A1 - Jhanji, Avantika A1 - Sydow, Benjamin A1 - Adams, Tom-Eric A1 - Habisch, Stefan A1 - Härtel, Sebastian T1 - Influence of the Initial Microstructure on the Mechanical Behavior During Forming for Inline Manufacturing Process Routes T2 - Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 2 N2 - 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. Y1 - 2023 SN - 978-3-031-40919-6 SN - 978-3-031-40920-2 U6 - https://doi.org/10.1007/978-3-031-40920-2_53 SN - 2195-4356 SP - 513 EP - 524 PB - Springer Nature Switzerland CY - Cham ER - TY - GEN A1 - Graf, Marcel A1 - Pippig, Robert A1 - Lehnert, Tim A1 - Jedynak, Angelika A1 - Härtel, Sebastian ED - Mocellin, Katia T1 - Aluminium-Matrix-Composites (AMC) for Hot Forged Components T2 - Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 1 N2 - 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. Y1 - 2023 SN - 978-3-031-41022-2 SN - 978-3-031-41023-9 U6 - https://doi.org/10.1007/978-3-031-41023-9_4 SN - 2195-4356 SP - 36 EP - 47 PB - Springer Nature Switzerland CY - Cham ER - TY - GEN A1 - Buhl, Johannes A1 - Härtel, Sebastian A1 - Besong, Lemopi Isidore ED - Mocellin, Katia T1 - Temperature Control of the Two-Point Incremental Forming Process to Achieve Homogeneous Martensite Content Based on Finite Element Simulations T2 - Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, ICTP 2023 - Volume 1 N2 - 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. Y1 - 2023 SN - 978-3-031-41022-2 SN - 978-3-031-41023-9 U6 - https://doi.org/10.1007/978-3-031-41023-9_74 SN - 2195-4356 SP - 739 EP - 747 PB - Springer CY - Cham ER - TY - GEN A1 - Grüger, Lennart A1 - Szyndler, Joanna A1 - Jensch, Felix A1 - Härtel, Sebastian T1 - Porosity analysis of L-PBF manufactured AZ91D components T2 - Materials research proceedings N2 - 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. KW - A91D KW - Additive Manufacturing KW - L-PBF KW - HIP KW - Process Parameter Analysis Y1 - 2025 SN - 978-1-64490-359-9 U6 - https://doi.org/10.21741/9781644903599-22 SN - 2474-395X VL - 54 SP - 199 EP - 208 PB - Materials Research Forum LLC CY - Millersville, PA ER - TY - GEN A1 - Sviridov, Alexander A1 - Alimov, Artem A1 - Jensch, Felix A1 - Dubinin, Sergej A1 - Härtel, Sebastian T1 - Influence of surface quality on performance of forging dies produced by additive manufacturing the role of post-processing in LPBF-manufactured X55 steel T2 - Materials research proceedings N2 - 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. KW - Additive manufacturing KW - L-PBF KW - Forging dies KW - Hot bulk forging KW - Friction KW - X55 Y1 - 2025 SN - 978-1-64490-359-9 U6 - https://doi.org/10.21741/9781644903599-27 SN - 2474-395X VL - 54 SP - 245 EP - 253 PB - Materials Research Forum LLC CY - Millersville, PA ER - TY - GEN A1 - Okolo, Chukwuemeka A1 - Eissing, Katharina A1 - Williams, Richard A1 - Jensch, Felix A1 - Fergani, Omar A1 - Härtel, Sebastian T1 - Investigation of the influence of AI-controlled process parameter adjustment on the mechanical properties of LBPF-manufactured parts T2 - Materials research proceedings N2 - 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. KW - LPBF-process KW - Machine learning KW - Mechanical properties Y1 - 2025 SN - 978-1-64490-359-9 U6 - https://doi.org/10.21741/9781644903599-24 SN - 2474-395X VL - 54 SP - 218 EP - 227 PB - Materials Research Forum LLC CY - Millersville, PA ER - TY - GEN A1 - Emdadi, Aliakbar A1 - Jensch, Felix A1 - Szyndler, Joanna A1 - Huang, Hsuan-Po A1 - Härtel, Sebastian A1 - Weiß, Sabine T1 - Void closure behavior during hot forming of an Fe-Al alloy T2 - Materials research proceedings N2 - 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. KW - Hot metal forming KW - Laser powder bed fusion (LPBF) KW - Post-processing KW - Void closure KW - X-Ray micro-computed tomography Y1 - 2025 SN - 978-1-64490-359-9 U6 - https://doi.org/10.21741/9781644903599-99 SN - 2474-395X VL - 54 SP - 927 EP - 935 PB - IWA Publishing CY - Millersville, PA ER - TY - GEN A1 - Ertugrul, Gökhan A1 - Emdadi, Aliakbar A1 - Härtel, Sebastian T1 - Advancements in iron aluminide alloy processing : a comparative study with DED alternatives T2 - Materials research proceedings N2 - 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. Y1 - 2025 U6 - https://doi.org/10.21741/9781644903599-28 SN - 2474-395X VL - 54 SP - 254 EP - 263 PB - Materials Research Forum LLC CY - Millersville, PA ER -