TY - CONF A1 - Schröpfer, Dirk T1 - Fachvortrag: Innovative Probenherstellungim Lichte der Proben-Bauteil-Beziehungen N2 - Der Vortrag erörtert die aktuellen fachlichen Herausforderungen und Ziele in der Zentralwerkstatt/FB9.2 der BAM für den Helmholtz-AK "Bau wissenschaftlicher Geräte" T2 - Helmholtz-Arbeitskreis "Bau wissenschaftlicher Geräte", 18. Jahrestagung CY - Berlin, Germany DA - 10.05.2023 KW - Probenfertigung KW - Erneuerbare Energien KW - Additive Fertigung KW - Wasserstoff-Sicherheit PY - 2023 AN - OPUS4-59263 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Beanspruchungen bei der Fertigung hochfester Komponenten N2 - Hochfeste und -warmfeste Legierungen nehmen in vielen Bereichen des Maschinen- und Anlagenbaus eine immer größere Rolle ein, deren Wirtschaftlichkeit und Effizienz durch eine kostensparende und präzise fügetechnische und abtragende Fertigung bestimmt wird. Komponenten aus modernen hochfesten Werkstoffen erfordern aufgrund ihres spezifischen Legierungskonzeptes und Gefüges und der oft hohen thermo-mechanischen Belastungen speziell adaptierte Fertigungsabläufe. Der Beitrag stellt einige Themenschwerpunkte vor, bei denen fertigungsbedingte Beanspruchungen und Eigenschaftsdegradationen an hochinnovativen Werkstoffen optimiert und wirtschaftliche Fertigungsbedingungen untersucht werden. T2 - Forschungsseminar OVGU CY - Magdeburg, Germany DA - 15.11.2018 KW - Eigenspannungen KW - MAG-Schweißen KW - Hochfeste Feinkornbaustähle KW - Bauteilprüfung KW - Zerspanung KW - HEA KW - Hochtemperaturwerkstoffe PY - 2018 AN - OPUS4-46608 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Beanspruchungen bei der Fertigung hochfester Komponenten N2 - Hochfeste und -warmfeste Legierungen nehmen in vielen Bereichen des Maschinen- und Anlagenbaus eine immer größere Rolle ein, deren Wirtschaftlichkeit und Effizienz durch eine kostensparende und präzise fügetechnische und abtragende Fertigung bestimmt wird. Komponenten aus modernen hochfesten Werkstoffen erfordern aufgrund ihres spezifischen Legierungskonzeptes und Gefüges und der oft hohen thermo-mechanischen Belastungen speziell adaptierte Fertigungsabläufe. Der Beitrag stellt einige Themenschwerpunkte vor, bei denen fertigungsbedingte Beanspruchungen und Eigenschaftsdegradationen an hochinnovativen Werkstoffen optimiert und wirtschaftliche Fertigungsbedingungen untersucht werden. T2 - Forschungsseminar, Access, Aachen CY - Aachen, Germany DA - 19.11.2018 KW - Bauteilprüfung KW - Eigenspannungen KW - Hochfeste Feinkornbaustähle KW - HEA KW - Hochtemperaturwerkstoffe KW - MAG-Schweißen KW - Zerspanung PY - 2018 AN - OPUS4-47723 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Beanspruchungsgerechtes ultraschallunterstütztes Fräsen Generativ gefertigter Turbinenbauteile N2 - Die Beschaffung und Verarbeitung von Werkstoffen für hochbelastete Komponenten sind meist kostenintensiv. Bestrebungen zur Kosten- und Ressourceneffizienz führen zu komplexeren Strukturen bzw. Konturen, sodass generative Fertigungsschritte zur Bauteilreparatur und -fertigung deutliche ökonomische Vorteile bieten. Hierfür sind generative und abtragende Fertigungsschritte komplementär und gezielt aufeinander abzustimmen, um beanspruchungsgerechte Funktionsflächen herzustellen. T2 - Forschungsseminar, TU Clausthal (ISAF) CY - Clausthal-Zellerfeld, Germany DA - 31.01.2018 KW - Eigenspannungen KW - Auftragschweißen KW - Zerspanung KW - Ultraschallunterstütztes Fräsen KW - Generative Fertigung PY - 2018 AN - OPUS4-47724 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Neues aus der BAM / Fachbereich 9.2 N2 - In dieser Präsentation werden die neuesten Herausforderungen und der Stand des Fachbereiches 9.2 für die Mitarbeit im AK des HGF "Bau wissenschaftlicher Geräte" dargestellt. Hierfür werden Neuigkeiten aus dem Bereich Materialprüfung in der BAM präsentiert und mit den Arbeiten der Zentralwerkstatt, die hierfür notwendig sind, in Zusammenhang gebracht. T2 - Helmholtz-Arbeitskreis "Bau wissenschaftlicher Geräte" CY - Berlin, Germany DA - 12.06.2024 KW - Fertigungsverfahren KW - Fertigungskompetenz PY - 2024 AN - OPUS4-62293 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Helmholtz-AK "Bau wissenschaftlicher Geräte" - Neues aus der BAM / Fachbereich 9.2 N2 - In dieser Präsentation werden die neuesten Herausforderungen und der Stand des Fachbereiches 9.2 für die Mitarbeit im AK des HGF "Bau wissenschaftlicher Geräte" dargestellt. T2 - Helmholtz-Arbeitskreis "Bau wissenschaftlicher Geräte", 18. Jahrestagung CY - Berlin, Germany DA - 10.05.2023 KW - Werkstatt KW - Erneuerbare Energien PY - 2023 AN - OPUS4-59262 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Studies on the pore formation in super duplex stainless steel welds N2 - When welding super duplex stainless steels a non-admissible pore formation can occur even if recommended processing guidelines are followed strictly. To investigate this phenomenon and to determine the influencing factors different claddings were produced using gas metal arc welding and submerged arc welding. The welding consumables, the shielding gas and the welding flux were varied. As shielding gases several mixtures, based on argon and 30 % helium, with various amounts of nitrogen, nitric oxide, carbondioxid and oxygen were applied. As welding flux agglomerated fluoride basic fluxes and aluminate fluoride basic fluxes were used. Different batches of the similar solid filler wire G 25 9 4 N L were used to produce the claddings on the base material UNS32750. To determine the pore formation X-ray examinations and microsections were used, to analyze the chemical composition of the claddings melt extractions and spectrometric examinations were applied. Additionally, the microhardness and the ferrite number were detected. The studies have shown the shielding gas, the welding flux and the filler metal possess a great influence on the pore formation. Even small variations in the chemical composition of the welding consumables lead to totally different results. In addition, the ferrite number and the chemical composition of the claddings depend strongly on the used gases and filler metals. T2 - IIW Intermediate Meeting, C-IIA CY - Madrid, Spain DA - 29.02.2016 KW - Cladding KW - Welding KW - Duplex stainless steels KW - Pore formation PY - 2016 AN - OPUS4-38786 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas T1 - Influence of the weld thermal cycle on residual stress evolution and cold cracking ressistance in welded high-strength steel constructions N2 - The application of high-strength fine-grained structural steels with yield stress ≥ 690 MPa permits significant weight reductions and cost savings. Since welding is the major joining technology, e.g. in mobile crane industry, the sustainable and economical application of these grades depends on the load-bearing capacity and safety of the welds. An economical processing of high-strength steels is determined above all by the avoidance of cold cracking, apart from achieving demand-oriented mechanical properlies in the weid area. High tensile residual stresses are disadvantageaus regarding the cold cracking resistance and strength of welded components. Furthermore, high restraints commonly appearing in component welds increase residual stresses. Hence, in this research the influences of heat control on residual stresses and the overall structural Ioad of welded structures were quantified. The relationship between the weid thermal cycle and the resulting residual stress under additional shrinkage restraint was analysed by a successive augmentation of the restraint intensity. This was achieved by systematic low Ioad and component weid tests. lt was observed that the heat control significantly affects the local residual stresses and the overall structural Ioad of welded structures. A high interpass temperature increases the global and local welding stresses in particular. Moreover, the transferability of experimental welding results obtained from small specimens according to applicable codes to real component geometries was investigated. With the help of these findings it is possible to improve existing heat control concepts for high-strength steel welding. T2 - 2nd METEC & ESTAD 2015 - European steel technology and application days conference CY - Düsseldorf, Germany DA - 15.06.2015 KW - Residual stresses KW - Welding KW - HEat control KW - GMAW KW - Restraint KW - High-strength steels KW - Cold cracking KW - MAG welding KW - Process parameters PY - 2015 SP - P668, 1 EP - 7 AN - OPUS4-34988 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Hamm, C. A1 - Röser, T. A1 - Michels, H. T1 - Vom Kokillenguss bis zur Fräsbearbeitung - Bauteile aus innovativen Eisen- und Titanaluminiden wirtschaftlich herstellen N2 - Der Beitrag gibt einen kurzen Einblick in das gerade bewilligte ZIM-Vorhaben „Technologie und Werkzeuge für ultraschallunterstütztes Fräsen von Eisen- und Titan-Aluminid-Bauteilen (TeWuFeAl)“. In dem Vorhaben wird durch 2 KMU aus dem Bereichen der Werkzeugentwicklung (Wolf GmbH) und der Anwendung (AWB GmbH) sowie durch 2 Forschungsinstitute, Access e. V. und Bundesanstalt für Materialforschung und -prüfung (BAM), die Herstellbarkeit sicherheitsrelevanter Leichtbauteile aus FeAl und TiAl durch das besonders wirtschaftliche Kokillengussverfahren und die anschließende ultraschallunterstützte Zerspanung untersucht. KW - Eisenaluminid KW - Titanaluminid KW - Kokillenguss KW - Fräsbearbeitung KW - Ultraschallunterstütztes Fräsen KW - Oberflächenintegrität PY - 2020 SP - 12 PB - Manufacturing Innovation Network e. V. CY - Varel, Germany AN - OPUS4-51593 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Reichel, Levin A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Modern welding processes for optimising repair welds on high strength offshore steels N2 - The successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future. To achieve these high outputs, turbines far from coast are required with large subsea jacket structures (30 m up to 50 m) and tall towers (up to 200 m). High-strength steels with a yield strength up to 500 MPa and wall thicknesses up to 150 mm are increasingly being used for these structures. This plac-es high demands on welding manufacturing, especially for high-strength offshore steels. During the manu-facturing process detected defects by NDT require localized repair of welds by gouging and rewelding. Due to a lack of investigations, there are no repair concepts and information in standards and guidelines, par-ticularly for high-strength thick plate joints made of high-strength offshore steels. However, these are ur-gently needed to enable manufacturers, especially SMEs, to carry out safe and economical repairs. There-fore, BAM started the FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair (local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal with controlled high-performance GMAW pro-cesses and optimized narrow gouging grooves. The experimental analyses take into account the complex interaction of process, material, and design-related influences on the formation of weld induced stresses and the special microstructure of high-strength fine-grain structural steels. Welding-related material degra-dation and crack-critical residual tensile stresses need to be avoided to ensure high component safety and performance. A reduction in residual stress in the presence of high restraint conditions can be achieved by adapted heat control (if no disassembly measures are possible). The repair process involves manual thermal gouging, which allows the groove configuration to be modi-fied. Modern welding processes using high frequency arc control provide deep root penetration and focused energy input capable of welding narrow seams. A comparison was made between the traditional weld con-figuration with a wide 45° groove and transition arc welding and a narrow 30° groove with modern welding process. Even in the case of free shrinkage specimens, the narrow groove weld exhibits a significant reduc-tion of residual stresses, cf. Figure 1, especially in the HAZ and toward the adjacent base material. This can be attributed to the lower weld metal volume needed and the reduction of heat input per layer due to the controlled arc process. For the purposes of this comparison, the same weld seam build-up (but different number of layers) has been applied to both seam configurations. Note that in industrial application (manu-al welding), the wider groove would be welded with several off-center weld beads with conventional weld-ing process. In this analysis this would cause asymmetric effects regarding the residual stress state, diffi-cult to compare to each other. Component-related welding experiments on special testing equipment, adapted process and heat control concepts along with variable groove configurations will be developed and recommendations for guidelines elaborated. This is the prerequisite for fully utilizing the strength potential of high-strength steels and making a valuable contribution to the energy transition in Germany, especially for steel-processing SMEs. T2 - IIW Intermediate Meeting CII CY - Trollhättan, Sweden DA - 10.03.2025 KW - Repair welding KW - Gouging KW - Residual stress KW - Offshore wind turbines KW - High-strength steels PY - 2025 AN - OPUS4-62743 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Findeisen, Dietmar A1 - Schröpfer, Dirk T1 - Energy efficiency in materials testing by reactive power part 2: resonance method in fatigue testing N2 - Reactive power is related to the type of power that does not consume energy but stores it. In the design of test machines, the utilization of this physical phenomenon would be very beneficial. Reactive power allows for the combination of power amplification with energy savings, making it an ideal principle for conducting long-term tests that involve high loads and prolonged energy consumption. This work focuses on testing machines operating in resonance, which allows for higher test frequencies and reduced test durations. Various types of fatigue testing machines, including those with rotating-unbalance actuators, servo-hydraulic actuators, and piezoelectric actuators, are examined through vibration analysis, methodical design, and mechatronics. Resonant testing machines provide significant advantages in energy efficiency and test accuracy for a wide range of applications in materials testing. These methods are crucial for future applications in industries where energy efficiency and precise fatigue testing are critical, such as aerospace, automotive, and civil engineering. KW - Reactive power KW - Amplitude magnification KW - Power amplification KW - Fatigue testing KW - Resonant test machines PY - 2024 DO - https://doi.org/10.1515/mt-2024-0350 SP - 1 EP - 11 PB - Walter de Gruyter GmbH AN - OPUS4-62356 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Findeisen, Dietmar A1 - Schröpfer, Dirk T1 - Energy efficiency in materials testing by reactive power – part 1: power recirculating method in wear testing N2 - Reactive power is related to the type of power that does not consume energy but stores it. In the design of test machines, the utilization of this physical phenomenon would be very beneficial. Reactive power allows for the combination of power amplification with energy savings, making it an ideal principle for conducting long-term tests that involve high loads and prolonged energy consumption. This concept is illustrated in this work focusing test machines used in rotary testing procedures. Drive element pairs, which serve as component test objects, are primarily exposed to wear stress. These stressed element pairs are consequently integral parts of a tribological system. The underlying principles of power amplification and power feedback are explained from the perspectives of drive technology, systematic design, methodical design, and mechatronics. KW - Reactive power KW - Power amplification KW - Power feedback KW - Wear testing KW - Strained element pairs PY - 2024 DO - https://doi.org/10.1515/mt-2023-0136 VL - 67 IS - 1 SP - 189 EP - 197 PB - Walter de Gruyter GmbH AN - OPUS4-62355 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Richter, Tim A1 - Delgado Arroyo, Diego A1 - Börner, Andreas A1 - Schröpfer, Dirk A1 - Rhode, Michael A1 - Lindner, T. A1 - Löbel, M. A1 - Preuß, B. A1 - Lampke, T. T1 - Ultrasonic assisted milling of a CoCrFeNi medium entropy alloy N2 - Medium and High Entropy Alloys (MEA/HEA) are recently developed material classes, providing manifold applications, e.g., due to extraordinary structural properties. In that connection, the machinability as important issue for the processing of these materials was not in the scientific focus. This study focusses on experimental analysis of milling process conditions including ultrasonic assisted milling (USAM) and their effects on the resulting surface integrity of equiatomic CoCrFeNi-MEA specimens. For that reason, milling parameters (cutting speed, feed per cutting edge) were systematically varied for both conventional milling and USAM. The surface integrity was analyzed in terms of topography, defects, and residual stresses. Especially USAM leads to a decrease of occurring cutting forces and, hence, to an improvement of the surface integrity. Beneficial effects were observed in terms of lower tensile residual stresses at high cutting speed and feed per cutting edge. KW - Medium entropy alloy KW - Ultrasonic Assisted Machining KW - Surface Integrity PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-554458 DO - https://doi.org/10.1016/j.procir.2022.05.203 VL - 108 SP - 879 EP - 884 PB - Elsevier B.V. AN - OPUS4-55445 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Rhode, Michael A1 - Wetzel, Annica A1 - Oczan, Ozlem A1 - Nietzke, Jonathan A1 - Richter, Tim A1 - Schröpfer, Dirk T1 - Corrigendum: Hydrogen diffusion and local Volta potential in high- and medium-entropy alloys (2020 IOP Conf. Ser.: Mater. Sci. Eng. 882 012015) N2 - In the sub-section “2.1 Investigated materials” the chemical composition of Co, Cr and Mn was in wrong order for both HEA and MEA. The content of table 1 is here included in the correct version. PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-527050 DO - https://doi.org/10.1088/1757-899X/882/1/012027 VL - 882 SP - 1 EP - 2 PB - IOP Publishing CY - Bristol AN - OPUS4-52705 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhode, Michael A1 - Erxleben, Kjell A1 - Richter, Tim A1 - Schröpfer, Dirk A1 - Mente, Tobias A1 - Michael, Thomas T1 - Local mechanical properties of dissimilar metal TIG welded joints of CoCrFeMnNi high entropy alloy and AISI 304 austenitic steel N2 - Multiple principal element alloys encompass the well-known high entropy alloys (HEA). The alloy system represents a new class of materials consisting of at least three alloying elements, each containing 5 to 35 at.%. Thus, this alloying concept differs fundamentally from conventional materials such as steel or nickel alloys. For this purpose, the alloying elements are specifically selected, the microstructures are adjusted in a single-phase and, in some cases, multi-phase manner. In particular, conflicting goals, such as the trade-off between strength and ductility in conventional steels, are overcome. However, in the last 20 years, the focus has been on material synthesis. With the increase in available material quantities, the focus is now on processing issues such as joining and welding processes. The weldability of HEAs has received very little attention so far. The experience with dissimilar metal welds is completely lacking but is essential for the application of these materials in combination with conventional materials. The present study presents comprehensive experimental results on the weldability of an equimolar CoCrFeMnNi-HEA in cold-rolled and heat-treated condition, which was joined by tungsten inert gas welding to an austenitic steel AISI 304. The mechanical properties of the dissimilar metal welds were characterized by cross-weld tensile samples, whereas the local deformation in the weld of the different welding zones was measured by digital image correlation. In accordance with the respective initial HEA condition (cold-rolled vs. heat-treated), the local strain behavior was divergent and influenced the global mechanical properties of both DMW types. Nonetheless, the experiments provided proof in principle of the weldability for dissimilar joints of the CoCrFeMnNi-HEA welded to conventional materials like austenitic stainless steels ensuring a corresponding capability for mechanical loading. This allows further considerations on the application of these innovative materials. KW - TIG welding KW - High-entropy alloys KW - Mechanical properties KW - Dissimilar metal weld PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-595775 DO - https://doi.org/10.1007/s40194-024-01718-4 SN - 0043-2288 SP - 1 EP - 11 PB - Springer Science and Business Media LLC AN - OPUS4-59577 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Richter, Tim A1 - Giese, Marcel A1 - Rhode, Michael A1 - Schröpfer, Dirk A1 - Michael, Thomas A1 - Fritsch, Tobias T1 - Influence of Surface Preparation on Cracking Phenomena in TIG-Welded High and Medium Entropy Alloys N2 - Multi-element systems with defined entropy (HEA—high entropy alloy or MEA—medium entropy alloy) are rather new material concepts that are becoming increasingly important in materials research and development. Some HEA systems show significantly improved properties or combinations of properties, e.g., the overcoming of the trade-off between high strength and ductility. Thus, the synthesis, the resulting microstructures, and properties of HEA have been primarily investigated so far. In addition, processing is crucial to achieve a transfer of potential HEA/MEA materials to real applications, e.g., highly stressed components. Since fusion welding is the most important joining process for metals, it is of vital importance to investigate the weldability of these materials. However, this has rarely been the subject of research to date. For that reason, in this work, the weldability depending on the surface preparation of a CoCrFeMnNi HEA and a CoCrNi MEA for TIG welding is investigated. The fusion welding of longer plates is described here for the first time for the CoCrNi alloy. The welds of both materials showed distinct formation of cracks in the heat affected Zone (HAZ). Optical and scanning electron microscopy analysis clearly confirmed an intergranular fracture topography. However, based on the results, the crack mechanism cannot be conclusively identified as either a liquid metal embrittlement (LME) or hot cracking-like liquid film separation. T2 - 2nd International Conference on Advanced Joining Processes CY - Sintra, Portugal DA - 21.10.2021 KW - TIG welding KW - Cracking KW - High entropy alloy KW - Medium entropy alloy KW - Surface preparation PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-541697 DO - https://doi.org/10.3390/jmmp6010005 SN - 2504-4494 VL - 6 IS - 5 SP - 1 EP - 13 PB - MDPI CY - Basel (CH) AN - OPUS4-54169 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Delgado Arroyo, Diego A1 - Richter, Tim A1 - Schröpfer, Dirk A1 - Boerner, Andreas A1 - Rhode, Michael A1 - Lindner, T. A1 - Preuß, B. A1 - Lampke, T. T1 - Influence of Milling Conditions on AlxCoCrFeNiMoy Multi-Principal-Element Alloys N2 - Multi-Principal-Element or High-Entropy Alloys (MPEAs/HEAs) have gained increasing interest in the past two decades largely due to their outstanding properties such as superior mechanical strength and corrosion resistance. However, research studies on their processability are still scarce. This work assesses the effect of different machining conditions on the machinability of these novel alloys, with the objective of advancing the introduction of MPEA systems into industrial applications. The present study focuses on the experimental analysis of finish-milling conditions and their effects on the milling process and resulting surface finish of CoCrFeNi, Al0.3CoCrFeNi and Al0.3CoCrFeNiMo0.2 alloys fabricated via Spark Plasma Sintering. Ball-nose-end milling experiments have been carried out various milling parameters such as cutting speed, feed per cutting edge, and ultrasonic assistance. In situ measurements of cutting forces and temperature on the tool edge were performed during the experiments, and surface finish and tool wear were analyzed afterwards. The results exhibited decreasing cutting forces by means of low feed per cutting edge and reduced process temperatures at low cutting speed, with the use of ultrasonic-assisted milling. It was shown that the machinability of these modern alloys through conventional, as well as modern machining methods such as ultrasonic-assisted milling, is viable, and common theories in machining can be transferred to these novel MPEAs. KW - Multi-principal element alloys KW - Finish milling KW - Spark plasma sintering KW - Ultrasonic-assisted milling KW - Microstructure characterization PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-572990 DO - https://doi.org/10.3390/coatings13030662 VL - 13 IS - 3 SP - 1 EP - 18 PB - MDPI (Multidisciplinary Digital Publishing Institute) CY - Basel (CH) AN - OPUS4-57299 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Buzolin, R.H. A1 - Richter, Tim A1 - Pixner, F. A1 - Rhode, Michael A1 - Schröpfer, Dirk A1 - Enzinger, N. T1 - Microstructure and texture characterisation of friction stir welded CoCrNi and CoCrFeMnNi multi-principle element alloys N2 - This work investigates the microstructure formed in friction stir welds of FCC alloys, focused on two multiprincipal alloys: a CoCrFeMnNi high-entropy alloy (HEA) and a CoCrNi medium-entropy alloy (MEA). A commercial stainless steel AISI 304 is used for comparison. The largest nugget was formed in the MEA, while the smallest was formed in the HEA. Grain refinement occurs in the stirred zone in all welds. Discontinuous dynamic recrystallisation is the predominant restoration mechanism during friction stir welding of the three investigated alloys. A sharp decrement in the Σ3 boundary fraction occurs in the stirred zone of the AISI 304 and HEA welds, while comparable values with the base metal are found for the MEA weld. The peak in the maximum index of crystallographic texture is observed on the advancing side of the stirred zone of the AISI 304 weld. A strong <001> θ-fibre texture is formed in the advancing side of the nugget in the AISI 304 from a well-established {123} <634> S-type texture in the base metal. Multiple crystallographic texture components without specific fibres are identified in most regions of the welds, indicating the complex shear path history during friction stir welding. KW - Microstructure KW - Multiple principal element alloy KW - Friction stir welding KW - Electron backscattered diffraction KW - Crystallographic texture PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-572987 DO - https://doi.org/10.1016/j.mtcomm.2023.105870 VL - 35 SP - 1 EP - 14 PB - Elsevier Ltd. CY - Amsterdam (NL) AN - OPUS4-57298 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Richter, Tim A1 - Diese, Marcel A1 - Rhode, Michael A1 - Schröpfer, Dirk T1 - Characterization of cracking phenomena in TIG welds of high and medium entropy alloy N2 - Multi-element systems with defined entropy (HEA - High Entropy Alloy or MEA - Medium Entropy Alloy) are rather new material concepts that are becoming increasingly important in materials research and development. Some HEA systems show significantly improved properties or combinations of properties, e.g., the overcome of the trade-off between high strength and ductility. Thus, the synthesis, the resulting microstructures, and properties of HEA have been primarily investigated so far. In addition, processing is crucial to achieve a transfer of potential HEA/MEA materials to real applications, e.g. highly stressed components. Since fusion welding is the most important joining process for metals, it is of vital importance to investigate the weldability of these materials. However, this has rarely been the subject of research up to date. For that reason, in this work the weldability depending on the surface preparation of a CoCrFeMnNi-HEA and a CoCrNi-MEA for TIG welding is investigated. The fusion welding of longer plates is described here for the first time for the CoCrNi alloy. The welds of both materials showed distinct formation of cracks in the heat affected zone (HAZ). Optical and scanning electron microscopy analysis clearly confirmed an intergranular fracture topography. But based on the results, the crack mechanism cannot be conclusively clarified as either a liquid metal embrittlement (LME) or hot cracking like liquid film separation occurred. T2 - 2nd International Conference on Advanced Joining Processes CY - Online meeting DA - 21.10.2021 KW - High Entropy Alloy KW - TIG welding KW - Cracking PY - 2021 AN - OPUS4-53607 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk T1 - Formation of multi-axial welding stresses due to material behaviour during fabrication of high-strength steel components N2 - Today an expanding application of high-strength steels in modern welded constructions can be observed. The economical use of these steel grades largely depends on the strength and reliability of the weldments. Therefore the special microstructure and mechanical properties of these grades have to be taken into account by keener working ranges regarding the welding parameters. However, performance and safety of welded components are strongly affected by the stresses occurring during and after welding fabrication locally in the weld seam and globally in the whole component, especially if the shrinkage and distortion due to welding are restrained. Some extensive studies describe the optimization of the welding stresses and the metallurgical effects regarding an adapted welding heat control. In particular lower working temperatures revealed to be effective to significantly reduce the local and global welding induced residual stresses of the completed weld. However, decreased interpass temperatures cause concurrently higher stresses during welding fabrication. This work shows some strategies to reduce these in-process stresses. With help of multi-axial welding stress analyses in component-related weld tests using a special 2-MN-testing facility differences in stress build-up are described in detail for root welds, filler layers and subsequent cooling to ambient temperature. T2 - IIW Intermediate Meeting, C-II-A CY - Trollhättan, Sweden DA - 06.03.2017 KW - Residual stresses KW - GMA Welding KW - High-strength steels KW - Process parameters KW - Restraint PY - 2017 AN - OPUS4-41066 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -