TY - JOUR A1 - Roveda, Ilaria A1 - Serrano-Munoz, Itziar A1 - Haubrich, J. A1 - Requena, G. A1 - Madia, Mauro T1 - Influence of post-process heat treatments on the fatigue crack propagation behaviour of a PBF-LB/M AlSi10Mg alloy N2 - The microstructure has a great influence on short fatigue crack growth in metallic materials. Laser-based Powder Bed Fusion AlSi10Mg alloys exhibit in the as-built condition a fine fibrous Si structure and a supersaturated solid solution of Si in the α-Al matrix, which is significantly modified by heat treatments starting already at temperatures under 260 °C. This study focuses on the influence of post-process heat treatments on the microstructural evolution and the resulting fatigue crack growth resistance. As compared to the as-built condition, two heat treatments at 265 °C/1 h and at 300 °C/2 h are found to be beneficial to the fatigue crack growth resistance of the investigated material. KW - Additive manufacturing KW - Fatigue crack growth KW - Cyclic R-curve KW - Heat treatment PY - 2023 DO - https://doi.org/10.1016/j.ijfatigue.2023.107808 SN - 0142-1123 VL - 175 SP - 1 EP - 12 PB - Elsevier Ltd. AN - OPUS4-57822 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Roveda, Ilaria T1 - Investigation of residual stresses and microstructure effects on the fatigue behaviour of a L-PBF AlSi10Mg alloy N2 - Al-Si alloys produced by Laser Powder Bed Fusion (L-PBF) techniques allow the fabrication of lightweight free-shape components. Due to the high cooling rates occurring during the building process, L-PBF AlSi10Mg alloys exhibit an ultra-fine microstructure that leads to superior mechanical properties in the as-built condition compared to conventional cast Al-Si materials. Nevertheless, L-PBF processing induces high thermal gradients, leading to deleterious residual stress. In order to relax detrimental residual stress and to increase the ductility, post-processing stress relief treatments are performed. The objective of the contribution is to investigate, under different heat treatment condition, the evolution of microstructure and residual stresses in view of optimizing the fatigue performance of the alloy. To this purpose various heat treatments in a range of temperatures between 265°C and 300°C for a duration between 15 minutes and 2 hours are performed. T2 - Fatigue Design 2021 CY - Senlis, France DA - 17.11.2021 KW - AlSi10Mg KW - Additive manufacturing KW - L-PBF KW - Residual stress KW - Heat treatment PY - 2021 AN - OPUS4-53794 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Engelking, Lorenz A1 - Eissel, A. A1 - Schröpfer, Dirk A1 - Treutler, K. A1 - Kannengießer, Thomas A1 - Wesling, V. T1 - Effect of alloy modification for additive manufactured Ni alloy components on microstructure and subsequent machining properties N2 - Ni alloys are generally classified as difficult-to-cut materials and cost intensive. Additive manufacturing (AM) offers economic advantages. However, machining of these AM components is mandatory to create the final contour or surface. The inhomogeneous and anisotropic microstructure and properties of AM components causes an unstable cutting process. Moreover, undesirable tensile residual stresses are generated due to subsequent machining. In this investigation, the initial alloy 36 is modified with Ti and Nb up to 1.6 wt.-% and build-up welded via gas metal arc welding (GMAW) and plasma-transferred-arc (PTA). Then, finish-milling tests are carried out to investigate the influence of the modification as well as the cutting parameters on the resulting cutting force and the surface integrity. In addition, the conventional milling process (CM) is compared with the ultrasonic-assisted milling process (US), which has a significant influence on the machinability as well as on the surface integrity. T2 - Additive Fertigung – Werkstoffe – Prozesse – Wärmebehandlung 2022 CY - Bremen, Germany DA - 29.06.2022 KW - Additive manufacturing KW - Alloy 36 KW - Alloy modification KW - Ultrasonic-assisted milling KW - Surface integrity PY - 2022 SP - 57 EP - 67 AN - OPUS4-55430 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scharf-Wildenhain, R. A1 - Hälsig, A. A1 - Hensel, J. A1 - Wandtke, Karsten A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Influence of Heat Control on Properties and Residual Stresses of Additive-Welded High-Strength Steel Components N2 - This contributed to the knowledge regarding the safe avoidance of cold cracking. In addition to a thermophysical simulation using a dilatometer of different high-strength steels with subsequent tensile testing, reference WAAM specimens (open hollow cuboids) were welded while utilizing a high-strength filler metal (ultimate tensile strength > 790 MPa). The heat control was varied by means of the heat input and interlayer temperature such that the Dt8/5 cooling times corresponded to the recommended processing range (approx. 5 s to 20 s). For the heat input, significant effects were exhibited, in particular on the local residual stresses in the component. Welding with an excessive heat input or deposition rate may lead to low cooling rates, and hence to unfavorable microstructure and component properties, but at the same time, is intended to result in lower tensile residual stress levels. Such complex interactions must ultimately be clarified to provide users with easily applicable processing recommendations and standard specifications for an economical WAAM of high-strength steels. These investigations demonstrated a major influence of the heat input on both the cooling conditions and the residual stresses of components manufactured withWAAM using high-strength filler materials. A higher heat input led to longer cooling times (Dt8/5) and approx. 200 MPa lower residual stresses in the surface of the top layer. KW - WAAM KW - Additive manufacturing KW - Heat control KW - High-strength filler metals KW - Residual stress PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-553982 UR - https://www.mdpi.com/2075-4701/12/6/951 DO - https://doi.org/10.3390/met12060951 VL - 12 IS - 6 SP - 951 PB - MDPI AN - OPUS4-55398 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Eissel, A. A1 - Engelking, Lorenz A1 - Treutler, K. A1 - Schröpfer, Dirk A1 - Wesling, V. A1 - Kannengießer, Thomas T1 - Investigations on influencing the microstructure of additively manufactured Co‑Cr alloys to improve subsequent machining conditions N2 - Co-Cr alloys are frequently used for highly stressed components, especially in turbine and plant construction, due to their high resistance to thermal and mechanical stress, as well as to corrosive and abrasive loads. Furthermore, they are classified as difficult-to-cut materials because of their high strength and toughness as well as their low thermal conductivity. However, for Co, an increased cost and supply risk can be observed in recent years. Therefore, additive manufacturing (AM) offers significant economic advantages due to higher material efficiency regarding repair, modification, and manufacturing of such components. Concerning inhomogeneity and anisotropy of the microstructure and properties as well as manufacturing-related stresses, a lot of knowledge is still necessary for the economic use of additive welding processes in SMEs. In addition, subsequent machining, particularly contour milling, is essential to generate the required complex contours and surfaces. Hence, additive and machining manufacturing processes need to be coordinated in a complementary way, especially due to additional challenges arising in milling of heterogeneous hard-to-cut microstructures. Recently, it has been shown that modern, hybrid cutting processes, such as ultrasonic-assisted milling (US), can improve the cutting situation. In this investigation, the Co-Cr initial alloy is additionally modified with Ti and Zr up to 1 wt% with the aim to enhance the homogeneity of the microstructure and, thus, the machinability. Hence the investigation includes finish milling tests of the AM components and the comparison of US and conventional machining. Both the modifications and the ultrasonic assistance exhibit a significant effect on the machining situation; for example US causes a higher surface integrity of the finish milled surfaces compared to conventional milling. T2 - International Congress on Welding, Additive Manufacturing and associated non-destructive testing CY - Online meeting DA - 08.06.2022 KW - Cobalt-chromium alloy KW - Additive manufacturing KW - Ultrasonic-assisted milling KW - Surface integrity PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-560917 DO - https://doi.org/10.1007/s40194-022-01397-z SP - 1 EP - 9 PB - Springer CY - Heidelberg AN - OPUS4-56091 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Residual stress formation in DED-arc manufactured high strength steel components N2 - Additive manufacturing (AM) processes enable the efficient production of advanced constructions. Direct energy deposition processes such as wire and arc-based additive manufacturing (DED-arc) are important methods. The wire filler metals enable a wide range of materials. In addition, the arc process provides a high deposition rate compared to laser and powder-based processes. Furthermore, components can be manufactured near-net-shape, offering significant savings in cost, time, and resources. Combined with the use of high-strength steels to reduce wall or component thicknesses in the context of lightweight design, great opportunities for saving energy and resources can be achieved. In a joint project of BAM and Chemnitz University of Technology, the main influences and complex interactions of material, production process, design and processing steps on the residual stress level are investigated. The aim is to develop processing recommendations and a cold cracking test for economical processing and stress-related design of high-strength steels with DED-arc. This study focuses on residual stress analysis by neutron diffraction (ND) and X-ray diffraction (XRD) on defined test specimens. The ND analysis were performed at the Paul Scherrer Institute (PSI) and the XRD analysis at BAM. The study shows a quantitative and qualitative comparison of the residual stress magnitudes and distribution between the component bulk (ND) and surface (XRD) analyses. The ND analysis reveals that in DED-arc AM walls the residual stresses dominate in the direction of welding and are negligibly small in each case transverse to the direction of welding. The topology of the analyzed residual stresses shows almost identical residual stress maps. In addition, the residual stresses are significantly influenced by the solid phase transformation of the material due to low cooling times in the area of the top layer. T2 - AJP 2023 3rd International Conference on Advanced Joining Processes CY - Braga, Portugal DA - 19.10.2023 KW - DED-arc KW - Residual stress KW - Neutron diffraction KW - High-strength steel KW - Additive manufacturing PY - 2023 AN - OPUS4-58647 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wandtke, Karsten T1 - Additive manufacturing of high-strength steel components using gas metal arc welding based direct energy deposition N2 - Additive manufacturing processes such as direct energy deposition-arc (DED-Arc) or Wire Arc Additive Manufacturing (WAAM) enable the efficient production of weight-optimized near-net-shape components in modern steel constructions [1,2]. Further increased efficiency can be achieved by using high-strength steels, which leads to significant cost, time, and resource savings. While commercial filler metals for arc welding processes are available, their industrial application is hindered by a lack of guidelines and quantitative knowledge of the welding stresses during production and operation limit their industrial application. In a joint project of BAM and Chemnitz University of Technology, the main influences and complex interactions of material, production process, design and processing steps on the residual stress level are investigated. The aim is to develop processing recommendations and a cold cracking test for economical processing and stress-related design of high-strength steels with DED-arc. The project focused on hardness and microstructure analysis as well as residual stress analysis using X-ray diffraction on the surface and neutron diffraction in the bulk. Reference specimens (open hollow cuboids) were fully automatic manufactured using a robot welding system. Systematic variation of the heat control and design was used to analyze the influences on heat input and interpass temperature, as well as geometric influences such as component length, height, and wall thickness. Figure 1 shows that the residual stresses in the WAAM specimens within the project are predominantly one-dimensional in welding direction (cf. [3]). Furthermore, the results reveal that the residual stresses are significantly influenced by the heat input. Low heat input and high cooling rates lead to high average residual stresses. The analysis of the variation of the component design indicates that the component height, in contrast to component length and wall thickness, significantly influences the level of residual stresses. T2 - Additive 2024 CY - Berlin, Germany DA - 12.06.2024 KW - High strength steels KW - Additive manufacturing KW - Residual stress PY - 2024 AN - OPUS4-61949 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Eissel, A. T1 - Investigations on influencing the microstructure of additively manufactured Co-Cr alloys to improve subsequent machining conditions N2 - Co-Cr alloys are frequently used for highly stressed components, especially in turbine and plant construction, due to their high resistance to thermal and mechanical stress, as well as to corrosive and abrasive loads. Furthermore, they are classified as difficult-to-cut materials because of their high strength and toughness as well as their low thermal conductivity. However, for Co, an increased cost and supply risk can be observed in recent years. Therefore, additive manufacturing (AM) offers significant economic advantages due to higher material efficiency regarding repair, modification, and manufacturing of such components. Concerning inhomogeneity and anisotropy of the microstructure and properties as well as manufacturing-related stresses, a lot of knowledge is still necessary for the economic use of additive welding processes in SMEs. In addition, subsequent machining, particularly contour milling, is essential to generate the required complex contours and surfaces. Hence, additive and machining manufacturing processes need to be coordinated in a complementary way, especially due to additional challenges arising in milling of heterogeneous hard-to-cut microstructures. Recently, it has been shown that modern, hybrid cutting processes, such as ultrasonic-assisted milling (US), can improve the cutting situation. In this investigation, the Co-Cr initial alloy is additionally modified with Ti and Zr up to 1 wt.-% with the aim to enhance the homogeneity of the microstructure and, thus, the machinability. Hence the investigation includes finish milling tests of the AM components and the comparison of US and conventional machining. Both the modifications and the ultrasonic assistance exhibit a significant effect on the machining situation, e.g., US causes a higher surface integrity of the finish milled surfaces compared to conventional milling. T2 - International Congress on Welding, Additive Manufacturing and associated non destructive testing CY - Online meeting DA - 08.06.2022 KW - Co-Cr-alloy KW - Additive manufacturing KW - Ultrasonic-assisted milling KW - Surface integrity PY - 2022 AN - OPUS4-55431 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Engelking, Lorenz T1 - Alloy modification for additive manufactured Ni alloy components Part II: Effect on subsequent machining properties N2 - Alloy 36 (1.3912), also known as “Invar”, is an alloy with 36% nickel. It was developed in 1897 by Guillaume and stands out for its very low thermal expansion coefficient. It is classified as a difficult-to-cut material and is commonly used for the production of fiber-reinforced composites in the field of mold construction. Additive manufacturing (AM) offers many economic advantages regarding the repair, modification and manufacture of entire components. Subsequent machining of the AM components is necessary to account for complex structures, final contours or defined surfaces. This is usually done using a tool with a geometrically defined cutting edge, i.e., milling processes. Surface integrity is determined by metallurgical (e.g., microstructure of the subsurface), topological (e.g., surface defects, roughness) and mechanical (e.g., residual stresses) factors, which is crucial in terms of component safety and performance. Modern, hybrid cutting processes, such as ultrasonic-assisted milling (US), provide potentially improvement of the cutting situation of these components. In part I of this investigation, the initial alloy 36 is modified with the elements Ti, Zr and Nb up to a maximum of 1 wt.-%. The influence of the modification elements on the microstructure as well as on the hardness of the AM components is examined. Part II focusses on the effect of the alloy modifications on machinability as well as on the surface integrity of plasma-transferred-arc-welded (PTA) and finish milled invar components. The results show a significant positive influence of ultrasonic assistance on the resulting cutting force of both materials. The modification with 1% Ti shows a positive influence on the surface integrity, as the roughness of the conventional machining processes is lower compared to the initial alloy, which has to be confirmed in further experiments. T2 - IIW C-II Intermediate meeting CY - Online meeting DA - 17.03.2022 KW - Alloy modification KW - Ultrasonic-assisted milling KW - Plasma-Transferred-Arc KW - Surface integrity KW - Alloy 36 KW - Additive manufacturing PY - 2022 AN - OPUS4-54910 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Engelking, Lorenz T1 - Alloy modification for additive manufactured Ni alloy components Part II: Effect on subsequent machining properties N2 - Alloy 36 (1.3912), also known as “Invar”, is an alloy with 36% nickel. It was developed in 1897 by Guillaume and stands out for its very low thermal expansion coefficient. It is classified as a difficult-to-cut material and is commonly used for the production of fiber-reinforced composites in the field of mold construction. Additive manufacturing (AM) offers many economic advantages regarding the repair, modification and manufacture of entire components. Subsequent machining of the AM components is necessary to account for complex structures, final contours or defined surfaces. In part I of this investigation, the initial alloy 36 is modified with the elements Ti, Zr and Hf up to a maximum of 0.33 wt.-%. The influence of the modification elements on the microstructure as well as on the hardness of the AM components is examined. Part II focusses on the effect of the alloy modifications on machinability as well as on the surface integrity of plasma-transferred-arc-welded (PTA) and finish milled invar components. Machining tests were carried out, to investigate the influence of ultrasonic assistance and the effects of modification elements Ti, Zr and Hf on the occurring cutting forces, temperatures and resulting surface integrity of the AM components made of alloy 36 and their modifications. The results show a significant positive influence of ultrasonic assistance on the resulting cutting force as well as on the roughness of all materials investigated. T2 - 75th IIW Annual Assembly CY - Tokyo, Japan DA - 17.07.2022 KW - Alloy modification KW - Alloy 36 KW - Additive manufacturing KW - Ultrasonic-assisted milling KW - Surface integrity PY - 2022 AN - OPUS4-55432 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Engelking, Lorenz T1 - Effect of alloy modification for additive manufactured Ni alloy components on microstructure and subsequent machining properties N2 - Ni alloys are generally classified as difficult-to-cut materials and cost intensive. Additive manufacturing (AM) offers economic advantages. However, machining of these AM components is mandatory to create the final contour or surface. The inhomogeneous and anisotropic microstructure and properties of AM components causes an unstable cutting process. Moreover, undesirable tensile residual stresses are generated due to subsequent machining. In this investigation, the initial alloy 36 is modified with Ti and Nb up to 1.6 wt.-% and build-up welded via gas metal arc welding (GMAW) and plasma-transferred-arc (PTA). Then, finish-milling tests are carried out to investigate the influence of the modification as well as the cutting parameters on the resulting cutting force and the surface integrity. In addition, the conventional milling process (CM) is compared with the ultrasonic-assisted milling process (US), which has a significant influence on the machinability as well as on the surface integrity. T2 - Additive Fertigung – Werkstoffe – Prozesse – Wärmebehandlung 2022 CY - Bremen, Germany DA - 29.06.2022 KW - Additive manufacturing KW - Alloy 36 KW - Alloy modification KW - Ultrasonic-assisted milling KW - Surface integrity PY - 2022 AN - OPUS4-55429 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Treutler, K. T1 - Nickel-iron-alloy modification to enhance additively welded microstructure for subsequent milling N2 - The aerospace industry uses nickel-iron-alloys to create moulding tools for composite materials because of the low coefficient of thermal expansion. These tools have a large-sized and complex structure, making them cost-intensive and difficult to manufacture. Therefore, the focus is set on additive manufacturing, which can additionally enable the repair of components in order to eliminate local defects. However, the process usually results in a heterogeneous microstructure and anisotropic mechanical properties. As there is a high demand for a precise and exact fit of the precision moulds and thus the surface quality, the welded components must be subsequently machined. Nickel-iron alloys are difficult to machine and an inhomogeneous microstructure also leads to unstable cutting forces. Consequently, a refinement and homogenisation of the microstructure morphology is achieved through specific alloy modifications in order to stabilise and improve the subsequent machining process. Studies on the refinement of FeNi 36 based on vacuum arc melting furnaces are used as a starting point. Therefore, titanium and niobium are chosen as modification elements with a maximum 1 % weight percent and are added to nickel-iron base alloy. The elements are alloyed and build-up welded by using plasma-transferred-arc welding. The resulting microstructure morphology of the welded wall structure and the machining properties are then determined. Furthermore, the influence on the coefficient of thermal expansion is investigated in connection with the modification and the welding process itself. It can be shown that even small amounts of niobium have a significant influence on the structural morphology of the welded layers during plasma-transferred-arc welding. T2 - 2nd international Conference on Advanced Joining Processes 2021 CY - Sintra, Portugal DA - 21.10.2021 KW - Alloy modification KW - Ultrasonic-assisted milling KW - Nickel-iron-alloy KW - Additive manufacturing KW - Plasma transferred arc welding PY - 2021 AN - OPUS4-53635 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael T1 - Joining processes for components in hydrogen technologies: Current need and future importance N2 - This presentation gives an overview on the importance of joining processes for component fabrication in hydrogen technologies. For that reason, the current need and future research and developement activites are highlighted for the three technological fields: hydrogen storage, transport and use (in terms of the emerging field of additive manufacturing). Finally, some remarks are given for necessary changes in the standardization. T2 - IIW Intermediate Meeting, Comm. II-A "Welding Metallurgy" CY - Online meeting DA - 17.03.2022 KW - Hydrogen KW - Welding KW - Research KW - Review KW - Additive manufacturing PY - 2022 AN - OPUS4-54488 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wandtke, Karsten T1 - Consideration of manufacturing-related stresses and cold crack avoidance in high-strength steels WAAM components N2 - High-strength steels offer great potential in weight-optimised modern steel structures. Additive manufacturing processes, such as Wire Arc Additive Manufacturing (WAAM), enable near-net-shape manufacturing of complex structures and more efficient manufacturing, offering significant savings in costs, time, and resources. Suitable filler materials for WAAM are already commercially available. However, the lack of knowledge or technical guidelines regarding welding residual stresses during manufacturing and operation in connection with cold cracking risk limit their industrial application significantly. In a project of BAM and TU Chemnitz, the influences and complex interactions of material, manufacturing process, design and processing steps on residual stress evolution are investigated. By developing process recommendations and a special cold cracking test, economic manufacturing, and stress-appropriate design of high-strength steel WAAM components are main objectives. The present study focuses on determining the influence of heat control (interpass temperature, heat input, cooling time) and the design aspects of the components on the hardness and residual stresses, which are analysed by X-ray diffraction. Defined reference specimens, i.e., hollow cuboids, are automatically welded with a special WAAM solid wire. The influences of wall length, wall thickness and wall height on the residual stresses are analysed. Geometric properties can be selectively adjusted by wire feed and welding speed but cannot be varied arbitrarily. This was addressed by adapted build-up strategies. The results indicate a significant influence of the heat control and the wall height on the residual stresses. The interpass temperature, wall thickness and wall length are not significant. These analyses allow recommendations for standards and manufacturing guidelines, enabling a safe and economic manufacturing of high-strength steel components. T2 - European Steel Technology and Application Days CY - Düsseldorf, Germany DA - 14.06.2023 KW - DED-arc KW - Additive manufacturing KW - Heat control KW - High-strength filler metals KW - Residual stress PY - 2023 AN - OPUS4-57691 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witte, Julien T1 - Optimizing residual stresses in additively manufactured high-performance materials N2 - The integration of modern high-performance materials in combination with additive manufacturing (AM) has revolutionized the approach to lightweight construction across diverse applications. This study explores the synergy between these materials and additive manufacturing (AM), focusing on their unique properties to engineer resource-efficient structures. Despite these advancements, machining these hard-to-cut materials such as iron-aluminide for safety-critical components remains challenging due to increased tool wear and compromised surface integrity. This research focuses on overcoming these challenges through the application of ultrasonic-assisted milling (USAM), a hybrid machining process exhibiting significant potential. By incorporating ultrasonic oscillations along the milling tool axis, USAM minimizes tool and component surface loads, enhancing tool life and producing defect-free, homogeneous surfaces with reduced roughness parameters. This investigation centers on the influence of ultrasonic-assisted milling on residual material stresses, crucial for component performance under load. In contrast to conventional milling generating tensile stresses, USAM induces advantageous compressive residual stresses, potentially enhancing the component's crack resistance. The study employs experimental variations in ultrasonic amplitude during the machining process to identify optimal parameters for achieving maximum compressive stresses. In addition, the depth profile of these residual stresses on the surface is investigated, which provides more detailed insights into their distribution and possible effects. This research not only contributes to the evolving environment of innovative manufacturing technologies, but also places particular focus on the central role of residual stresses in the performance and reliability of safety-critical AM components. The results not only contribute to a better understanding of ultrasonic-assisted milling, but also provide crucial guidance for the design of components that can withstand the challenges of real-world applications. T2 - European Conference on Surface Integrity 11 CY - Prague, Czech Republic DA - 03.06.2024 KW - Ultrasonic-assisted milling KW - Additive manufacturing KW - High-performance materials KW - Surface integrity KW - Residual stresses depth profile PY - 2024 AN - OPUS4-62026 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Treutler, Kai T1 - Additive Manufacturing of Iron Aluminides: Microstructure, Machinability, and Surface Integrity N2 - The increasing global focus on energy and resource efficiency has stimulated a growing interest in additive manufacturing. AM offers economic advantages and enables an efficient use of materials. However, AM components often require subsequent mechanical post-processing, such as machining (e.g. milling), to achieve the final contours or surfaces. This is a particular challenge due to the heterogeneous and anisotropic nature of AM structures, which affect machining and the resulting component properties. High-performance materials such as iron aluminide represent a promising alternative to conventional high-temperature materials with a significant economic advantage. However, the strength and hardness properties, which are advantageous for applications in highly stressed lightweight components, pose a challenge for economical machining in addition to the AM microstructure properties. The difficult-to-cut material causes accelerated tool wear and insufficient surface quality. This study shows that crack-free additive manufacturing of the three-component system of iron-nickel-aluminum is possible and advantages in terms of machinability compared to FeAl-AM components are achieved. The more homogeneous microstructure leads to a reduction in cutting forces, with positive effects on the machinability and optimized surface integrity. Ultrasonic assisted milling (USAM) offers great potential to address the major challenges posed by difficult-to-cut materials and additively manufactured weld structures. Therefore, this study focuses on assessing the transferability of previous positive results by USAM to the selected iron aluminide alloys. The machinability of the aluminides is analyzed by varying significant influencing variables in finish milling experiments and evaluated in terms of the loads on the tool and the resulting surface integrity. T2 - Intermediate Meeting of IIW CY - Online meeting DA - 13.03.2024 KW - Additive manufacturing KW - Surface-integrity KW - Iron-aluminide KW - Ultrasonic-assisted milling KW - Difficult-to-cut KW - Tool wear PY - 2024 AN - OPUS4-62294 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wandtke, Karsten T1 - Influence of machining on residual stresses in additive manufactured high-strength steel components N2 - Additive manufacturing processes such as direct energy deposition-arc (DED-Arc) welding or Wire Arc Additive Manufacturing (WAAM) enable the efficient production of weight-optimized near-net-shape components in modern steel constructions. Further increased efficiency can be achieved by using high-strength steels. This enables considerable savings in terms of costs, time and resources. Commercial filler metals are available for these arc welding processes, but a lack of guidelines and quantitative knowledge of the welding stresses during production and operation limit their industrial application. This study focuses on the effect of machining steps on the residual stresses and distortion of WAAM specimens. These specimens were welded fully automatically with a special WAAM solid wire (yield strength >820 MPa) with different geometric designs. The initial state and the state after cutting of the residual stresses were analyzed by means of X-ray diffraction on the surface and compared with data from three-dimens T2 - IIW Annual Assembly 2024 CY - Rhodos, Greece DA - 07.07.2024 KW - High strength steels KW - Additive manufacturing KW - Residual stress PY - 2024 AN - OPUS4-61951 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Engelking, Lorenz T1 - Optimisation of surface residual stresses using hybrid milling processes for additive manufactured Ni alloy components N2 - Ni alloys are cost intensive materials and generally classified as difficult-to-cut materials. However, machining of these materials is needed especially in case of alloy 36 (1.3912), which is commonly used in mould construction for the production of fibre-reinforced composites. With regard to repair, modification and manufacturing of such components, additive manufacturing offers significant economic advantages. Nevertheless, subsequent machining steps are needed to achieve the final component contour and defined surface conditions. Dependent on the material and machining process conditions, detrimental tensile residual stresses may be the result on the machined surface, having negative impact on the component performance and safety. Recent studies exhibited that hybrid machining processes, such as ultrasonic-assisted milling (USAM), are suitable for achieving favourable residual stress states at the surface of difficult-to-cut Ni-Cr alloys. In this investigation, wire arc additive manufactured (WAAM) specimens of alloy 36 were finish milled under different milling conditions. In addition to the machined surfaces condition and topology, the surface-near residual stresses were analysed using X-ray diffraction (XRD). Especially for low cutting speeds, significantly improved surface properties, roughness parameters and lower mechanical and microstructural degradations were found for the specimen machined with USAM compared to conventional milling. The improved surface integrity could furthermore be observed by a significant reduction of the tensile residual stresses in the surface boundary area. T2 - ICRS11, 11th International Conference on Residual Stresses CY - Nancy, France DA - 27.03.2022 KW - Surface integrity KW - Ultrasonic-assisted milling KW - Additive manufacturing KW - Ni alloy KW - Alloy 36 PY - 2022 AN - OPUS4-54904 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander T1 - RS analysis in laser powder bed fused austenitic stainless steel N2 - The determination of residual stress in additively manufactured materials is a challenge, even after decades from the establishment of the basics of residual stress analysis. This is due to the peculiar microstructure of such materials. In fact, researchers have discovered that conventional methods for the determination of RS in materials do not properly work for AM materials. In this tutorial, the basics of RS analysis will be explained, together with the basics of AM manufacturing techniques. The microstructure of the peculiar materials (AM) dealt with here will be elucidated. Successively, the necessary modifications to the conventional approaches to RS analysis will be explained and case studies will be displayed, for the attendant to touch with hands the peculiarities of the approaches. Finally, a few experimental and theoretical tips will be given on dos and don’ts for a correct determination of RS in AM materials. T2 - 11th edition of the European Conference on Residual Stress (ECRS11) CY - Prague, Czech Republic DA - 03.06.2024 KW - Residual stress KW - Additive manufacturing KW - Diffraction KW - Laser Powder Bed Fusion KW - AGIL KW - 316L PY - 2024 AN - OPUS4-60445 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Influence of Ultrasonic-Assisted Milling on Surface Integrity of Additively Manufactured Components Using DED-Arc/GMAW N2 - Additive manufacturing (AM) is increasingly used for producing complex metallic com-ponents. Subsequent machining is essential to achieve final geometries and surface conditions. The resulting surface integrity, particularly the near-surface residual stress state, plays a crucial role in component performance and fatigue life. This study inves-tigates the potential of ultrasonic-assisted milling (USAM), a hybrid machining process, to improve surface integrity and machinability compared to conventional milling (CM). Three materials were investigated, two difficult-to-cut materials CoCr26Ni9Mo5W and FeNi36 and a low-alloy steel S355J2C. The CoCr26Ni9Mo5W and FeNi36 were addi-tively manufactured via DED-Arc and then machined with varying cutting speeds and feed rates within a Design of Experiments. USAM exhibited enhanced machinability and surface integrity, particularly at low cutting speeds, by reducing cutting forces up to 40% and shifting near-surface residual stresses from tensile to compressive. For S355J2C, USAM reduced cutting forces by approximately 45% and induced surface-near compressive residual stresses up to approximately -700 MPa, leading to a 11% higher fatigue strength compared to CM. These findings highlight the advantages of ultrasonic assistance in post-AM machining, offering enhanced fatigue performance and surface quality for various metallic materials. T2 - 4th International Conference on Advanced Joining Processes 2025 CY - Coimbra, Portugal DA - 16.10.2025 KW - Ultrasonic-assisted milling KW - Additive manufacturing KW - Surface integrity KW - Fatigue strength KW - Residual stress PY - 2025 AN - OPUS4-65051 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witte, Julien A1 - Treutler, Kai A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Influence of Microstructure on the Machinability and Surface Integrity of Additively Manufactured Iron Aluminides N2 - The increasing global focus on energy and resource efficiency has stimulated a growing interest in additive manufacturing. AM offers economic advantages and enables an efficient use of materials. However, AM components often require subsequent mechanical post-processing, such as machining (e.g. milling), to achieve the final contours or surfaces. This is a particular challenge due to the heterogeneous and anisotropic nature of AM structures, which affect machining and the resulting component properties. High-performance materials such as iron aluminide represent a promising alternative to conventional high-temperature materials with a significant economic advantage. However, the strength and hardness properties, which are advantageous for applications in highly stressed lightweight components, pose a challenge for economical machining in addition to the AM microstructure properties. The difficult-to-cut material causes accelerated tool wear and insufficient surface quality. This study shows that crack-free additive manufacturing of the three-component system of iron-nickel-aluminum is possible, and advantages in terms of machinability compared to FeAl-AM components are achieved. The more homogeneous microstructure leads to a reduction in cutting forces, with positive effects on the machinability and optimized surface integrity. Ultrasonic assisted milling (USAM) offers great potential to address the major challenges posed by difficult-to-cut materials and additively manufactured weld structures. Therefore, this study focuses on assessing the transferability of previous positive results by USAM to the selected iron aluminide alloys. The machinability of the aluminides is analyzed by varying significant influencing variables in finish milling experiments and evaluated in terms of the loads on the tool and the resulting surface integrity. T2 - AA Meeting of Commission IX ‘Behavior of Metals subject to Welding’ CY - Rhodes, Greece DA - 08.07.2024 KW - Iron aluminide KW - Additive manufacturing KW - Machinability KW - Surface integrity KW - Ultrasonic-assisted milling PY - 2026 SP - 1 EP - 16 AN - OPUS4-65530 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ferrari, Bruno A1 - Fantin, Andrea A1 - Said, D. A1 - Fitch, A. N. A1 - Suárez Ocano, Patricia A1 - Mishurova, Tatiana A1 - Roveda, Ilaria A1 - Kromm, Arne A1 - Darvishi Kamachali, Reza A1 - Bruno, Giovanni A1 - Evans, Alexander A1 - Requena, G. A1 - Agudo Jácome, Leonardo A1 - Serrano Munoz, Itziar T1 - The impact of scanning strategy on cell structures in PBF-LB/M/IN718: an in situ synchrotron x-ray diffraction study N2 - In additive manufacturing, any change of the process parameters, such as scanning strategy, directly affects the cooling rates, heat accumulation, and overall thermal history of the build. Consequently, parts built with different process parameters tend to have different levels of crystallographic texture, residual stress, and dislocation density. These features can influence the properties of the material and their development during post-processing operations. In this study, IN718 prisms were built by laser powder bed fusion (PBF-LB/M) using two different scanning strategies (continuous 67° rotations around the build direction, ROT, and alternating 0°/67° scans, ALT) to provide two different as-built conditions. In situ time-resolved synchrotron diffraction was performed during a solution heat treatment at 1027 °C for 1 h. Ex situ scanning electron microscopy was used to support and complement the in situ observations. An approach to quantify the effect of elemental microsegregation at the cell walls is developed based on the deconvolution of asymmetric γ-nickel matrix peaks. Following this approach, the scanning strategies are shown to affect the as-built fraction of cell walls in the material, resulting in a difference of approximately 5 %, in weight fraction, between ROT and ALT (19 % vs. 24 %, respectively). This microsegregation was observed to be rapidly homogenized during the heating ramp, and no significant changes to the peak shape in the γ peaks occurred during the isothermal part of the heat treatment, regardless of the scanning strategy. KW - Additive manufacturing KW - Inconel 718 KW - Synchrotron x-ray diffraction KW - Heat treatment KW - Laser powder bed fusion KW - Cellular microstructure PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-650958 DO - https://doi.org/10.1016/j.jmrt.2025.11.214 SN - 2238-7854 VL - 41 SP - 593 EP - 608 PB - Elsevier B.V. AN - OPUS4-65095 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander T1 - Manufacturing a safer world: Diffraction based residual stress analysis for metal additive manufacturing N2 - Metal Additive Manufacturing (AM) technologies such as Laser Powder Bed Fusion (LPBF) are characterized by layer wise construction, which enable advancements of component design, with associated potential gains in performance and efficiency. However, high magnitude residual stresses (RS) are often a product of the rapid thermal cycles typical of the layerwise process. Therefore, a deep understanding of the formation of RS, the influence of process parameters on their magnitude and the impact on mechanical performance is crucial for widespread application. The experimental characterisation of these RS is essential for safety related engineering application and supports the development of reliable numerical models. Diffraction-based methods for RS analysis using neutrons and high energy X-rays enable non-destructive spatially resolved characterisation of both surface and bulk residual stresses in complex components. This presentation will provide an overview of recent research by the BAM at large scale facilities for the characterization of residual stresses in LPBF metallic alloys as a function of process parameters. In addition, the challenges posed by the textured and hierarchical microstructures of LPBF materials on diffraction-based RS analysis in AM materials will be discussed. This will include the question of the d0 reference lattice spacing and the appropriate choice of the diffraction elastic constants (DECs) to calculate the level of RS in LPBF manufactured alloys. T2 - 11th INternational Conference on Residual Stress (ICRS11) CY - Online meeting DA - 28.03.2021 KW - Residual stress analysis KW - Neutron diffraction KW - X-ray diffraction KW - Additive manufacturing KW - Laser powder bed fusion KW - AGIL PY - 2022 AN - OPUS4-54676 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Bruno, Giovanni A1 - Buffière, J.-Y. A1 - Wegener, T. A1 - Niendorf, T. A1 - Wu, T. A1 - Zhang, X. A1 - Kashaev, N. A1 - Meneghetti, G. A1 - Hrabe, Nik A1 - Madia, Mauro A1 - Werner, Tiago A1 - Hilgenberg, Kai A1 - Koukolikova, M. A1 - Prochazka, R. A1 - Dzugan, J. A1 - Möller, B. A1 - Beretta, S. A1 - Evans, Alexander A1 - Wagener, R. A1 - Schnabel, K. T1 - Damage tolerant design of additively manufactured metallic components subjected to cyclic loading: State of the art and challenges N2 - This article is an outcome of a workshop on Fatigue of Additive Manufactured Metallic Components jointly organized by the Federal Institute for Materials Research and Testing (BAM) Berlin, Germany and the National Institute of Standards and Technology (NIST) Boulder, CO, U.S.A. The aim of the workshop was a comprehensive discussion of the specific aspects of additively manufactured (AM) components in regard to failure under cyclic loading. Undoubtedly, a better understanding and the further development of approaches for damage tolerant component design of AM parts are among the most significant challenges currently facing the use of these new technologies. This article presents a thorough overview of the workshop discussions. It aims to provide a review of the parameters affecting the damage tolerance of AM parts with special emphasis on the process parameters intrinsic to the AM technologies, the resulting defects and residual stresses. Based on these aspects, concepts for damage tolerant component design for AM are reviewed and critically discussed. KW - Additive manufacturing KW - Fatigue loading KW - Component assessment KW - Damage tolerance KW - Defects KW - Residual stresses PY - 2021 DO - https://doi.org/10.1016/j.pmatsci.2021.100786 SN - 0079-6425 VL - 121 PB - Elsevier CY - Amsterdam AN - OPUS4-51937 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander T1 - Ageing behaviour of laser powder bed fused 316L: a powder to failure approach N2 - Laser powder bed fusion (LPBF) is an additive manufacturing process for materials which inherently tends to yield various degrees of metastable hierarchical microstructures, defects and high residual stresses in the as-built condition depending on the process parameters. The understanding of the evolution of these typical features during heat treatment and subsequent thermal and mechanical ageing is crucial for the wider acceptance for safety critical structures. A multi-disciplinary research project at BAM studying the development of the microstructure, defects, residual stresses typical of LPBF 316L and their evolution during thermal and mechanical ageing has led to insights into the stability of these inherent features. This presentation aims to give a broad overview of the project with a few specific cases of investigation. Firstly, the formation of residual stresses, the nature of the initial microstructure, the tensile properties and a modelling approach to understand the anisotropy will be presented. This will be followed by examples of studies of their evolution during heat treatment, long term thermal exposure, and room temperature and high temperature mechanical testing compared to a baseline of conventional wrought variant of the same alloy. T2 - International Conference on Additive Manufacturing 2021 (ICAM 2021) CY - Online meeting DA - 01.11.2021 KW - Ageing KW - Additive manufacturing KW - Laser powder bed fusion KW - AGIL PY - 2021 AN - OPUS4-54106 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Jakob A1 - Evans, Alexander A1 - Luzin, V. A1 - Abreu Faria, G. A1 - Degener, Sebastian A1 - Polatidis, E. A1 - Čapek, J. A1 - Kromm, Arne A1 - Dovzhenko, G. A1 - Bruno, Giovanni T1 - Texture-based residual stress analysis of laser powder bed fused Inconel 718 parts N2 - Although layer-based additive manufacturing methods such as laser powder bed fusion (PBF-LB) offer an immense geometrical freedom in design, they are typically subject to a build-up of internal stress (i.e. thermal stress) during manufacturing. As a consequence, significant residual stress (RS) is retained in the final part as a footprint of these internal stresses. Furthermore, localized melting and solidification inherently induce columnar-type grain growth accompanied by crystallographic texture. Although diffraction-based methods are commonly used to determine the RS distribution in PBF-LB parts, such features pose metrological challenges in their application. In theory, preferred grain orientation invalidates the hypothesis of isotropic material behavior underlying the common methods to determine RS. In this work, more refined methods are employed to determine RS in PBF-LB/M/IN718 prisms, based on crystallographic texture data. In fact, the employment of direction-dependent elastic constants (i.e. stress factors) for the calculation of RS results in insignificant differences from conventional approaches based on the hypothesis of isotropic mechanical properties. It can be concluded that this result is directly linked to the fact that the {311} lattice planes typically used for RS analysis in nickel-based alloys have high multiplicity and less strong texture intensities compared with other lattice planes. It is also found that the length of the laser scan vectors determines the surface RS distribution in prisms prior to their removal from the baseplate. On removal from the baseplate the surface RS considerably relaxes and/or redistributes; a combination of the geometry and the scanning strategy dictates the sub-surface RS distribution. KW - Additive manufacturing KW - Electron backscattered diffraction KW - Principal stress KW - Residual stress PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-578331 DO - https://doi.org/10.1107/S1600576723004855 SN - 1600-5767 VL - 56 IS - Pt 4 SP - 1076 EP - 1090 AN - OPUS4-57833 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ulbricht, Alexander T1 - Separation of the Formation Mechanisms of Residual Stresses in LPBF 316L N2 - Rapid cooling rates and steep temperature gradients are characteristic of additively manufactured parts and important factors for the residual stress formation. This study examined the influence of heat accumulation on the distribution of residual stress in two prisms produced by Laser Powder Bed Fusion (LPBF) of austenitic stainless steel 316L. The layers of the prisms were exposed using two different border fill scan strategies: one scanned from the centre to the perimeter and the other from the perimeter to the centre. The goal was to reveal the effect of different heat inputs on samples featuring the same solidification shrinkage. Residual stress was characterised in one plane perpendicular to the building direction at the mid height using Neutron and Lab X-ray diffraction. Thermography data obtained during the build process were analysed in order to correlate the cooling rates and apparent surface temperatures with the residual stress results. Optical microscopy and micro computed tomography were used to correlate defect populations with the residual stress distribution. The two scanning strategies led to residual stress distributions that were typical for additively manufactured components: compressive stresses in the bulk and tensile stresses at the surface. However, due to the different heat accumulation, the maximum residual stress levels differed. We concluded that solidification shrinkage plays a major role in determining the shape of the residual stress distribution, while the temperature gradient mechanism appears to determine the magnitude of peak residual stresses. T2 - MLZ User Meeting 2020 CY - Online meeting DA - 08.12.2020 KW - Computed tomography KW - Neutron diffraction KW - X-ray diffraction KW - Additive manufacturing KW - Residual stress KW - Thermography KW - LPBF KW - Laser Powder Bed Fusion PY - 2020 AN - OPUS4-51793 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Mishurova, Tatiana A1 - Thiede, Tobias A1 - Sprengel, Maximilian A1 - Kromm, Arne A1 - Nadammal, Naresh A1 - Nolze, Gert A1 - Saliwan Neumann, Romeo A1 - Evans, Alexander A1 - Bruno, Giovanni T1 - The residual stress in as‑built Laser Powder Bed Fusion IN718 alloy as a consequence of the scanning strategy induced microstructure N2 - The effect of two types of scanning strategies on the grain structure and build-up of Residual Stress (RS) has been investigated in an as-built IN718 alloy produced by Laser Powder Bed Fusion (LPBF). The RS state has been investigated by X-ray diffraction techniques. The microstructural characterization was performed principally by Electron Backscatter Diffraction (EBSD), where the application of a post-measurement refinement technique enables small misorientations (< 2°) to be resolved. Kernel average misorientation (KAM) distributions indicate that preferably oriented columnar grains contain higher levels of misorientation, when compared to elongated grains with lower texture. The KAM distributions combined with X-ray diffraction stress maps infer that the increased misorientation is induced via plastic deformation driven by the thermal stresses, acting to self-relieve stress. The possibility of obtaining lower RS states in the build direction as a consequence of the influence of the microstructure should be considered when envisaging scanning strategies aimed at the mitigation of RS. KW - Additive manufacturing KW - LPBF KW - Residual stress KW - Inconel 718 KW - Kernel average misorientation KW - Texture PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-511769 DO - https://doi.org/10.1038/s41598-020-71112-9 VL - 10 IS - 1 SP - 14645 AN - OPUS4-51176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander T1 - Diffraction based residual stress analysis for laser powder bed fusion alloys N2 - Laser Powder Bed Fusion (PBF-LB/M) is a layer wise metal additive manufacturing (AM) technology, which enables significant advancements of component design, leading to potential efficiency and performance improvements. However, the thermal cycles inherent to the process comprising large localized thermal gradients and repeated melting and solidification cycles leads to the generation of high magnitude residual stresses. These residual stresses can be detrimental both during manufacturing of components and in subsequent application. Therefore, a deep understanding of the influence of process parameters on the residual stresses are crucial for efficient manufacturing and safe application. The experimental characterization of these residual stresses is therefore crucial and can provide a reliable baseline for simulations of both the process and applications. Diffraction-based methods for residual stress analysis using penetrating neutrons and high energy X-rays enable non-destructive spatially resolved characterization of both surface and bulk residual stresses. However, the unique microstructural features inherent to the process can challenge some of our assumptions when using these methods. These challenges include the determination of a stress-free reference, the use of correct elastic constants (both SCEC and DEC) and the influence of surface roughness, texture, and porosity on residual stresses. This presentation will detail recent insights and recommendations for the characterization of residual stresses in a range of PBF-LB/M metallic alloys (Fe, Ni, Al and Ti) T2 - 11th edition of the European Conference on Residual Stress (ECRS11) CY - Prague, Czech Republic DA - 03.06.2024 KW - Residual stress KW - Additive manufacturing KW - Laser Powder Bed Fusion KW - Diffraction PY - 2024 AN - OPUS4-60443 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sprengel, Maximilian A1 - Ulbricht, Alexander A1 - Evans, Alexander A1 - Kromm, Arne A1 - Sommer, Konstantin A1 - Werner, Tiago A1 - Kelleher, J. A1 - Bruno, Giovanni A1 - Kannengießer, Thomas T1 - Towards the optimization of post-laser powder bed fusion stress-relieve treatments of stainless steel 316L N2 - This study reports on the stress relaxation potential of stress-relieving heat treatments for laser powder bed fused 316L. The residual stress is monitored non-destructively using neutron diffraction before and after the heat treatment. Moreover, the evolution of the microstructure is analysed using scanning electron microscopy. The results show, that a strong relaxation of the residual stress is obtained when applying a heat treatment temperature at 900°C. However, the loss of the cellular substructure needs to be considered when applying this heat treatment strategy. KW - Residual stress KW - Additive manufacturing KW - Neutron diffraction KW - Projekt AGIL - Alterung additiv gefertigter metallischer Materialien und Komponenten PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-536045 DO - https://doi.org/10.1007/s11661-021-06472-6 SN - 1543-1940 VL - 52 IS - 12 SP - 5342 EP - 5356 PB - Springer CY - Boston AN - OPUS4-53604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nadammal, Naresh A1 - Mishurova, Tatiana A1 - Fritsch, Tobias A1 - Serrano-Munoz, Itziar A1 - Kromm, Arne A1 - Haberland, C. A1 - Portella, Pedro Dolabella A1 - Bruno, Giovanni T1 - Critical role of scan strategies on the development of microstructure, texture, and residual stresses during laser powder bed fusion additive manufacturing N2 - Laser based powder bed fusion additive manufacturing offers the flexibility to incorporate standard and userdefined scan strategies in a layer or in between the layers for the customized fabrication of metallic components. In the present study, four different scan strategies and their impact on the development of microstructure, texture, and residual stresses in laser powder bed fusion additive manufacturing of a nickel-based superalloy Inconel 718 was investigated. Light microscopy, scanning electron microscopy combined with electron backscatter diffraction, and neutron diffraction were used as the characterization tools. Strong textures with epitaxially grown columnar grains were observed along the build direction for the two individual scan strategies. Patterns depicting the respective scan strategies were visible in the build plane, which dictated the microstructure development in the other planes. An alternating strategy combining the individual strategies in the successive layers and a 67◦ rotational strategy weakened the texture by forming finer microstructural features. Von Mises equivalent stress plots revealed lower stress values and gradients, which translates as lower distortions for the alternating and rotational strategies. Overall results confirmed the scope for manipulating the microstructure, texture, and residual stresses during laser powder bed fusion additive manufacturing by effectively controlling the scan strategies. KW - Additive manufacturing KW - Laser powder bed fusion KW - Nickel-based superalloys KW - Scan strategies KW - Residual stresses KW - Microstructure and texture PY - 2021 DO - https://doi.org/10.1016/j.addma.2020.101792 VL - 38 SP - 1792 PB - Elsevier B.V. AN - OPUS4-51944 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Roveda, Ilaria A1 - Serrano-Munoz, Itziar A1 - Mishurova, Tatiana A1 - Madia, Mauro A1 - Pirling, T. A1 - Evans, Alexander A1 - Klaus, M. A1 - Haubrich, J. A1 - Requena, G. A1 - Bruno, Giovanni T1 - Influence of a 265 °C heat treatment on the residual stress state of a PBF-LB/M AlSi10Mg alloy N2 - Laser Powder Bed Fusion (PBF-LB/M) additive manufacturing (AM) induces high magnitude residual stress (RS) in structures due to the extremely heterogeneous cooling and heating rates. As the RS can be deleterious to the fatigue resistance of engineering components, great efforts are focused on understanding their generation and evolution after post-process heat treatments. In this study, one of the few of its kind, the RS relaxation induced in an as-built PBF-LB/M AlSi10Mg material by a low-temperature heat treatment (265 °C for 1 h) is studied by means of X-ray and neutron diffraction. Since the specimens are manufactured using a baseplate heated up to 200 °C, low RS are found in the as-built condition. After heat treatment a redistribution of the RS is observed, while their magnitude remains constant. It is proposed that the redistribution is induced by a repartition of stresses between the a-aluminium matrix and the silicon phase, as the morphology of the silicon phase is affected by the heat treatment. A considerable scatter is observed in the neutron diffraction RS profiles, which is principally correlated to the presence (or absence) of pockets of porosity developed at the borders of the chessboard pattern. KW - Neutron diffraction KW - Additive manufacturing PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-565115 DO - https://doi.org/10.1007/s10853-022-07997-w SN - 1573-4803 VL - 57 SP - 22082 EP - 22098 PB - Springer Science + Business Media CY - Dordrecht AN - OPUS4-56511 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander T1 - Residual Stresses in Additive Manufacturing (L-PBF) N2 - Metal Additive manufacturing (AM) technologies such as Laser Powder Bed Fusion (LPBF) enable the fabrication of complex structures, giving rise to potential improvements in component and manufacturing efficiency. However, the processes are typically characterized by the generation of high magnitude residual stress (RS) which can have detrimental consequences for subsequent applications. Therefore, the characterization of these RS fields and the understanding of their formation and mitigation through optimized processing is crucial for the wider uptake of the technology. Due to the potential complex nature and high value of components manufactured by LPBF, it is important to have suitable characterisation methods which can determine the spatial variations of RS in a non-destructive manner. Neutron diffraction is considered to be the best suited for these requirements. However, the microstructures developed in the complex thermal cycles experience in the production can pose challenges to the ND method for RS analysis. The BAM has conducted significant research over the past years to overcome these obstacles, enabling higher confidence in the RS determined in LPBF materials by neutron diffraction. This contribution will overview some of these advancements made recently at European neutron sources including on Stress-Spec at FRM2/MLZ. T2 - MLZ User Meeting 2021 CY - Online meeting DA - 07.12.2021 KW - Residual stress KW - Additive manufacturing KW - Diffraction KW - AGIL KW - Manufact PY - 2021 AN - OPUS4-54044 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander T1 - Residual Stresses in Additive Manufacturing (L-PBF) N2 - Additive manufacturing (AM) technologies are experiencing an exceedingly rapid growth, driven by their potential through layer wise deposition for transformational improvements of engineering design, leading to efficiency and performance improvements. Laser Powder Bed Fusion (LPBF) is an Additive Manufacturing (AM) method which permits the fabrication of complex structures that cannot otherwise be produced via conventional subtractive manufacturing methods. Nevertheless, the rapid cooling rates associated with this process results in the formation of significant and complex residual stress (RS) fields. A large body of both experimental and simulation research has been dedicated in recent years to the control and mitigation of RS in AM. In order to validate simulations with the end goal of being able to model the residual stress state in AM components and to devise strategies for their reduction during manufacturing, experimental methods need to be able to accurately determine 3D residual stresses fields in complex geometries. Several destructive and non-destructive methods can be used to analyze the RS state, the choice of which depends on the geometry and the information required. Diffraction-based methods using penetrating neutron and synchrotron X-rays at large scale facilities offer the possibility to non-destructively spatially resolve both surface and bulk residual stresses in complex components and track their changes following applied thermal or mechanical loads. This presentation will overview the success stories of using large scale facilities by the BAM for the characterization of residual stresses in additively manufactured metallic alloys. In particular, the study of the influence of process parameters on the residual stress state and the relaxation of these stresses through heat treatment will be presented. However there remains challenges to overcome particularly of the hypotheses underlying the experimental determination of residual stresses, which will be discussed. T2 - 10th International Conference on Mechanical Stress Evaluation by Neutron and Synchrotron Radiation – MECASENS 2021 CY - Prague, Czech Republic DA - 25.11.2021 KW - Residual stress KW - Additive manufacturing KW - Diffraction KW - L-PBF KW - AGIL PY - 2021 AN - OPUS4-54105 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Evans, Alexander T1 - Residual stresses Analysis in Additively Manufactured alloys using neutron diffraction (L-PBF) N2 - An overview of recent progress at BAM of residual stress analysis in additively manufactured, in particular Laser Powder Bed Fusion of metallics materials, using neutron diffraction will be presented. This will cover important topics of the stress-free reference, the diffraction elastic moduli and principal stress determination. T2 - AWT-Fachausschuss 13 "Eigenspannungen" CY - Berlin, Germany DA - 28.03.2023 KW - AGIL KW - Residual stress KW - Additive manufacturing KW - Laser Powder Bed Fusion KW - Diffraction PY - 2023 AN - OPUS4-59177 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Scharf-Wildenhain, R. T1 - Influence of build up height on residual stresses in additive repair and modification using DED Arc N2 - Directed Energy Deposition (DED)-Arc is suitable for the hybrid additive manufacturing, modification and repair of large metal components with high deposition rates. Residual stresses and distortion are of central importance when characterizing the manufactured components and the sensitive transition area between AM component and semi-finished product. Residual stresses caused by the thermal cycles during the manufacturing process can impair the mechanical properties of the manufactured parts and can lead component failure. Therefore, understanding and controlling residual stresses, especially when combining different base and filler materials, is critical to improving the quality and efficiency of the hybrid DED-Arc process. This article deals with the influence of the build-up height on the residual stress distribution of additively manufactured components with a selected base and filler material combination. Using a robot-assisted DEDsystem and a controlled short arc, systematic step cancellation tests were carried out at a selected working temperature (200 C°) and heat input (600 kJ/m). In a 5-stage termination experiment, straight walls were produced using a one bead per layer strategy and selected increasing component heights between 15 mm and 300 mm. The influence of the build height on the longitudinal residual stress in the process direction was analyzed and discussed. All experiments showed a comparable stress distribution in the area of the substrate plate up to the heat-affected zone (HAZ) and the transition zone, regardless of the buliding height. However, the height showed a significant influence on the of residual stress distribution of the deposited AM-component. High positive stress gradients with a maximum range between 300 MPa to 400 MPa were always found in the last approx. 18 component layers (upper 40 mm), which can be explained by the shrinkage of the nonheat- treated top layer. Underlying layers, where present, showed a homogeneous residual stress distribution characterized by low compressive stresses. This can be explained by the process related tempering during the deposition of the upper layers. A constant boundary layer number was determined for all specimens. Once this number was exceeded, the distribution of residual stresses no longer changed, but merely shifted with the increasing height of the component in the direction of build-up. These correlations contribute to the understanding of residual stress development with increasing structure height. This study is part of a running research project on the properties of hybrid additive components and processes. It aims the stress optimized hybrid additive manufacturing of high-strength components and the necessary recommendations for application. T2 - 78th IIW Annual Assembly and International Conference on Welding and Joining CY - Genoa, Italy DA - 22.06.2025 KW - DED-Arc KW - Additive manufacturing KW - Residual stress PY - 2025 AN - OPUS4-65192 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Witte, Julien A1 - Treutler, Kai A1 - Schroepfer, Dirk A1 - Kannengiesser, Thomas A1 - Wesling, Volker T1 - Influence of microstructure on the machinability and surface integrity of additively manufactured iron aluminides N2 - The increasing global focus on energy and resource efficiency has stimulated a growing interest in additive manufacturing. AM offers economic advantages and enables an efficient use of materials. However, AM components often require subsequent mechanical post-processing, such as machining (e.g., milling), to achieve the final contours or surfaces. This is a particular challenge due to the heterogeneous and anisotropic nature of AM structures, which affect machining and the resulting component properties. High-performance materials such as iron aluminide represent a promising alternative to conventional high-temperature materials with a significant economic advantage. However, the strength and hardness properties, which are advantageous for applications in highly stressed lightweight components, pose a challenge for economical machining in addition to the AM microstructure properties. The difficult-to-cut material causes accelerated tool wear and insufficient surface quality. This study shows that crack-free additive manufacturing of the three-component system of iron-nickel-aluminum is possible, and advantages in terms of machinability compared to FeAl-AM components are achieved. The more homogeneous microstructure leads to a reduction in cutting forces, with positive effects on the machinability and optimized surface integrity. Ultrasonic assisted milling (USAM) offers great potential to address the major challenges posed by difficult-to-cut materials and additively manufactured weld structures. Therefore, this study focuses on assessing the transferability of previous positive results by USAM to the selected iron aluminide alloys. The machinability of the aluminides is analyzed by varying significant influencing variables in finish milling experiments and evaluated in terms of the loads on the tool and the resulting surface integrity. KW - Iron aluminide KW - Additive manufacturing KW - Machinability KW - Surface integrity KW - Ultrasonic-assisted milling process PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-656993 DO - https://doi.org/10.1007/s40194-026-02382-6 SN - 0043-2288 SP - 1 EP - 13 PB - Springer Science and Business Media LLC AN - OPUS4-65699 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -