@article{64678, abstract = {{One of the major topics in the modern automotive industry is reducing emissions and increasing the mileage range. To tackle this challenge, on the one hand, modifying the powertrain system is a possibility, and on the other hand, lightweight design offers various possibilities. Multi-Material Design (MMD) involves designing car bodies that combine different materials that require joining. Given the variety of materials, mechanical joining processes are preferred. Especially the current development of the Giga/Mega-casting process concerning aluminium casting and the subsequent mechanical joining illustrates the challenges of this material group. In car production, aluminium castings are mainly made from aluminium-silicon (AlSi) alloys. Ultimately, the alloy system's insufficient ductility leads to crack initiation during mechanical joining. Cast parts are therefore often used in areas of the car body that are exposed to high-pressure loads. For example, self-piercing riveting (SPR) is used due to its high load-bearing capacity. In this study, improved joinability is demonstrated by influencing the microstructure through tailored solidification rates and a developed heat-treatment chain strategy adapted for hypoeutectic AlSi systems. Data on microstructure, mechanical, and joining properties are used to develop a solidification-joining correlation for the SPR process across a range of Si contents and solidification rates. The purpose is to develop the ability to produce suitable aluminium castings with sufficient joinability, thereby improving versatility.}}, author = {{Neuser, Moritz and Kaimann, Pia Katharina and Stratmann, Ina and Bobbert, Mathias and Klöckner, Johann Moritz Benedikt and Mann, Moritz and Hoyer, Kay-Peter and Meschut, Gerson and Schaper, Mirko}}, journal = {{Journal of Manufacturing Processes}}, keywords = {{Mechanical joining, Aluminium, Self-piercing riveting, Casting, Microstructure, Joinability AlSi-alloys}}, publisher = {{Elsevier}}, title = {{{Solidification-joinability correlation of hypoeutectic aluminium casting alloys for self-piercing riveting (SPR)}}}, doi = {{https://doi.org/10.1016/j.jmapro.2026.02.040}}, volume = {{164}}, year = {{2026}}, } @article{58807, abstract = {{One of the most important strategies for reducing CO2 emissions in the mobility sector is lightweight construction. In particular, the car body offers several opportunities for weight reduction. Multi-material designs are increasingly being applied to select the most suitable material for the respective load and ultimately achieve synergy effects. For example, aluminium castings are used at the nodes of a spaceframe body. Subsequently, these are joined with profiles to form the bodyshell. To join different materials mechanical joining techniques, such as semi-tubular self-piercing riveting, are deployed. According to the current state of the art, cracks occur in the aluminium castings during the mechanical joining process as a result of the high degree of deformation. Although the aluminium casting alloys of the AlSi-system exhibit low ductility, these alloys reveal excellent castability. In particular, the ability to cast thin structural parts is enabled by the low liquidus point of the near eutectic aluminium casting alloys. This study addresses the mechanical joining properties of the near eutectic aluminium casting alloy AlSi12, depending on different microstructures. These are achieved by annealing processes and modifying agents. Through an adapted heat treatment, the previously lamellar morphology can be transformed into a globular morphology, which leads to increased ductility and prevents the formation of cracks during the self-piercing riveting (SPR). The joinability is investigated using different die geometries, whereas the joint formation is analysed regarding crack initiation. To evaluate the increased ductility, microstructural and mechanical tests are performed and finally, a microstructure-joinability correlation is established.}}, author = {{Neuser, Moritz and Holtkamp, Pia Katharina and Hoyer, Kay-Peter and Kappe, Fabian and Yildiz, Safak and Bobbert, Mathias and Meschut, Gerson and Schaper, Mirko}}, journal = {{The Journal of Materials: Design and Applications, Part L}}, keywords = {{aluminium, casting, microstructure, joinability, self-piercing riveting}}, location = {{Porto, Portugal}}, publisher = {{Sage Publications}}, title = {{{Mechanical properties and joinability of the near-eutectic aluminium casting alloy AlSi12}}}, doi = {{10.1177/14644207251319922}}, year = {{2025}}, } @inproceedings{49437, abstract = {{The phase and TTT diagrams of the Ti-6Al-4V system allow the development of a new forming process for a more energy- and materialefficient production of sheet metal parts. This new “TISTRAQ” process is composed of two steps. In terms of process technology, the first step is comparable to a direct press-hardening process already well known for steels. In this step, the Ti-6Al-4V sheet material is resistively heated to a temperature below β-transus Tβ and, after a very short holding time, simultaneously formed and quenched by use of water cooled tools. Thereby, the β phase undergoes a martensitic transformation. The second step is a subsequent short-time annealing, which leads to a hardening of the material. In this work, a new test rig using resistive heating technique was used in order to produce different solution treated and tool quenched (STQ) and subsequently annealed (STA) states. In this paper, the effects of heating rate, solution treatment temperature and holding time on microstructure and mechanical properties are addressed. For the characterisation, tensile testing and scanning electron microscopy were used. By the systematic variation of applied processing parameters, dominating effects on microstructure and mechanical properties were evaluated. For example, the solution treatment temperature was found to have a significant effect on microstructural features and characteristic strength and strain values. The obtained results reveal a high potential for future technical applications.}}, author = {{Pfeffer, Nina and Kaiser, Maximilian Alexander and Meyer, Thomas and Göken, Mathias and Höppel, Heinz Werner}}, booktitle = {{IOM3. Chapter 14: Forming, Machining & Joining [version 1; not peer reviewed]}}, keywords = {{Ti-6Al-4V, thermomechanical processing, resistive heating, quench-forming, process parameter-microstructure-properties relationship}}, location = {{Edinburgh}}, title = {{{The new TISTRAQ process: Solution treatment with rapid quenching and annealing for Ti-6Al-4V sheet metal part forming - the effect of processing parameters on microstructure and mechanical properties}}}, doi = {{https://doi.org/10.7490/f1000research.1119929.1}}, year = {{2024}}, } @article{29196, abstract = {{In biomedical engineering, laser powder bed fusion is an advanced manufacturing technology, which enables, for example, the production of patient-customized implants with complex geometries. Ti-6Al-7Nb shows promising improvements, especially regarding biocompatibility, compared with other titanium alloys. The biocompatible features are investigated employing cytocompatibility and antibacterial examinations on Al2O3-blasted and untreated surfaces. The mechanical properties of additively manufactured Ti-6Al-7Nb are evaluated in as-built and heat-treated conditions. Recrystallization annealing (925 °C for 4 h), β annealing (1050 °C for 2 h), as well as stress relieving (600 °C for 4 h) are applied. For microstructural investigation, scanning and transmission electron microscopy are performed. The different microstructures and the mechanical properties are compared. Mechanical behavior is determined based on quasi-static tensile tests and strain-controlled low cycle fatigue tests with total strain amplitudes εA of 0.35%, 0.5%, and 0.8%. The as-built and stress-relieved conditions meet the mechanical demands for the tensile properties of the international standard ISO 5832-11. Based on the Coffin–Manson–Basquin relation, fatigue strength and ductility coefficients, as well as exponents, are determined to examine fatigue life for the different conditions. The stress-relieved condition exhibits, overall, the best properties regarding monotonic tensile and cyclic fatigue behavior.}}, author = {{Hein, Maxwell and Kokalj, David and Lopes Dias, Nelson Filipe and Stangier, Dominic and Oltmanns, Hilke and Pramanik, Sudipta and Kietzmann, Manfred and Hoyer, Kay-Peter and Meißner, Jessica and Tillmann, Wolfgang and Schaper, Mirko}}, issn = {{2075-4701}}, journal = {{Metals}}, keywords = {{General Materials Science, Metals and Alloys, laser powder bed fusion, Ti-6Al-7Nb, titanium alloy, biomedical engineering, low cycle fatigue, microstructure, nanostructure}}, number = {{1}}, publisher = {{MDPI AG}}, title = {{{Low Cycle Fatigue Performance of Additively Processed and Heat-Treated Ti-6Al-7Nb Alloy for Biomedical Applications}}}, doi = {{10.3390/met12010122}}, volume = {{12}}, year = {{2022}}, } @article{34438, abstract = {{The sealing capabilities of RSS do not only depend on the seal itself but also on the lubricant and the shaft surface. A twist structure on the surface can cause pumping of the fluid during shaft rotation which can result in leakage. In this paper a special, new turning method, which consists of at least two turning steps with feed in reciprocal direction, is presented as an alternative to the conventional manufacturing process. The goal is to create a surface structure with a net pumping rate of zero. Shafts turned with the new proposed method are compared to turned shafts from previous investigations [1]. Criteria for the comparison are the surface pumping rate, leakage and wear behavior of the surface.}}, author = {{Thielen, Stefan and Magyar, Balázs and Sauer, Bernd and Schneider, Frank and Mayer, Patrick and Kirsch, Benjamin and Müller, Ralf and v. Harbou, Erik and Aurich, Jan C.}}, issn = {{0301-679X}}, journal = {{Tribology International}}, keywords = {{Radial shaft seals, Turned surfaces, Microstructure}}, pages = {{442--450}}, title = {{{Functional investigation of zero lead radial shaft seal counter-surfaces turned with a special method}}}, doi = {{https://doi.org/10.1016/j.triboint.2017.02.002}}, volume = {{118}}, year = {{2018}}, } @inproceedings{9870, abstract = {{Nowadays wire bonding is a widely-used technology for interconnecting chips in the packaging industry. Thereby, it is known that the bond quality massively depends upon the microstructure prevailing in the bond and consequently the materials used as well as the bonding parameters. However the actually used materials such as aluminum and gold are either characterized by comparibly poor conductivity or high costs, respectively. Due to its outstanding properties copper is a more attractive candidate. Still, a thorough investigation on the interrelationship between the material combinations, the processing parameters and the resulting microstructure for copper and aluminum wire bonding was not carried out yet. Depending on the aforementioned factors the microstructural evolution can be completely different during the bonding process. Therefore, this study focuses on the microstructural evolution of heavy copper and heavy aluminum wires bonded on copper substrates. The evolution of the wire microstructure as well as the wire-substrate-interface was investigated by scanning electron microscope in combination with electron backscatter diffraction and microhardness measurements. Various samples were extracted at different points of the bonding process, namely the as-received condition, after touchdown and after completed bonding. The results of the aluminum and copper wires were compared to each other in both longitudinal and transversal direction. It was found, that the two wire materials were completely different in the as-received condition regarding the grain size, the grain morphology, the texture and the microhardness. After touchdown the microstructure did not show significant changes in both materials, yet a strain-hardening was observed in the copper wire resulting from the touchdown force. When the bonding process was completed a different microstructure could be observed in both the wire as well as the layer for the materials investigated. Furthermore, a destinctive increase in the wire hardness could be found in case of copper, which was not observed for the aluminum wire. The ramifications between the two wire materials presented in this work will be discussed with the objective of optimizing the quality of the bonds.}}, author = {{Eacock , Florian and Schaper, Mirko and Althoff, Simon and Unger, Andreas and Eichwald, Paul and Hengsbach, Florian and Zinn, Carolin and Holzweissig, Martin Joachim and Guth, Karsten}}, booktitle = {{Proceedings of the 47th International Symposium on Microelectronics}}, keywords = {{Bonding, Copper, Microstructure evolution}}, title = {{{Microstructural investigations of aluminum and copper wire bonds}}}, doi = {{10.4071/isom-THP32}}, year = {{2014}}, }