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Forged high-performance components form the basis of technical innovations in the energy and transport sector. Great efforts are undertaken to develop new materials for forging, aiming at optimizing both the material performance and the effort needed for materials processing. The development of new forging alloys is accomplished using computational methods in combination with experimental techniques. The experimental characterization is time-consuming and requires a significant material effort. In high-alloy grades, inevitable segregations occur during casting which require substantial efforts for homogenizing the alloys by annealing and forging. In this work, gas atomization of powder and Selective Laser Melting (SLM) is explored as a new means to provide small, homogeneous samples of the desired alloys at reduced processing times. In this regard, gas atomization is used to produce raw material for SLM, which is used to prepare the specimens for the analysis of forging process parameters. The Waspaloy is considered in this work. SLM and conventional specimens are compared by means of hot isostatic compression tests in a dilatometer to determine the flow stress and microstructure evolution. The work shows that thermomechanical treatment of the as-printed state allows to convert the additive manufactured (AM) microstructures into structures that are useful inferring on the forging properties of the considered alloy., Procedia Manufacturing, 47, ISSN:2351-9789, 23rd International Conference on Material Forming

Efficient lightweight solutions are of great interest in many industries (aviation, automotive) particularly regarding the limitation of CO2-emissions and material waste. An innovative strategy to address these challenges is the use of hybrid manufacturing. Additive manufacturing (laser metal deposition, LMD) and conventional forming methods (hole-flanging) are used to optimize and functionalize AA 6016 sheet metal parts, which are widely used in the manufacturing of car body parts. First of all, the effects of the additive reinforcements on the mechanical and microstructural properties are investigated using tensile and microstructural tests. After manufacturing reinforced blanks and performing subsequent forming operations, the parts are investigated regarding damages and functionalized through threading. This allows the application of a bolt connection, which is tested through rip-off tests to evaluate the effect of the reinforcements on the fracture forces. It can be shown, that reinforcements can be manufactured without defects and virtually no porosity and the formability is only slightly reduced compared to conventional materials. At the same time, the performance of the reinforced bolt joint can be enhanced while the increase in weight can be limited to relatively small amounts., Production Engineering, 15 (2)

Additive manufacturing (AM) offers the possibility of locally reinforcing sheet metal or sheet metal products by adding patches that are metallurgically bonded to the substrate. Due to the high design freedom of AM, patches can be easily adapted to loads in geometry and thickness. However, the heat input and the high cooling rates during AM processes have a strong influence on the microstructure in the patch as well as in the substrate, which will affect forming properties. The aim of this work is to investigate the influence of patches produced by laser material deposition (LMD) on formability of micro-alloyed sheet metals. After determining a suitable process window for metallurgically bonded patches without cracks and pores, investigations were carried out on the microstructure and mechanical properties of reinforced samples. This work includes metallographic examinations using optical microscopy, hardness measurements and tensile tests. The formability of sheets with local reinforcement was investigated by stretching and Nakajima tests. The heat input creates a heat affected zone (HAZ) directly next to the patches with a reduced strength, caused by recrystallization that may lead to failure in the forming process and thus limits the forming capacity of locally reinforced sheet metals. A subsequent laser heat treatment can homogenize the properties in the HAZ., Procedia Manufacturing, 47, ISSN:2351-9789, 23rd International Conference on Material Forming

Additive manufacturing (AM) processes such as Wire-Arc Additive Manufacturing (WAAM) are highly flexible and particularly suited for manufacturing complex geometries in small batch-sizes. In the case of large batch-sizes, the low production rate of WAAM is a bottleneck, and therefore forming processes with higher production rates are more suitable. However, forming processes such as closed die forging require dedicated tooling and hence lack the flexibility needed to produce product variants. The current study proposes to combine additive manufacturing with forging to form hybrid components with high complexity and acceptable production rates. This is particularly advantageous for parts that are produced in variants. However, the main challenge in achieving a combination of these manufacturing technologies is the design of the process chain, ensuring that the final properties meet the specifications of the part. In this regard, the process sequence of forming followed by WAAM is investigated. The base material EN AW-6082 was formed to a preform by forging, followed by the deposition of different aluminum alloys by WAAM. The evolution of mechanical properties such as hardness and microstructure was analyzed. Based on the experimental observations, strategies to improve the performance of the hybrid components are presented., Procedia Manufacturing, 47, ISSN:2351-9789, 23rd International Conference on Material Forming

Wire-arc additive manufacturing is an additive manufacturing technology which allows for high deposition rates and is well suited for manufacturing larger parts in a short time compared to other additive manufacturing technologies. The technology has already received considerable industrial take-up for various materials and applications. The aim of this work is to investigate the alloy EN AW 6016 as wire stock for WAAM. To establish this, aluminum wire was produced by wire drawing. Using this wire, specimens were produced on base plate material using a variety of process parameters. These parts were then used to evaluate the mechanical properties. Further properties such as porosity and hardness were investigated using light optical microscopy. Based on the results, the potential of the alloy for WAAM of lightweight parts is discussed., Procedia Manufacturing, 47, ISSN:2351-9789, 23rd International Conference on Material Forming

Mechanical joining processes provide various advantages over conventional fusion welding of metallic components such as shorter cycle times, little or no heat input and reduced need for subsequent surface finishing operations. Several investigations in the past have shown that joints between tubes and sheets or plates can be manufactured by upsetting operations. Under axial compression, the tube develops a plastic instability in form of bulge. In-between two such bulges, a force and form fit to sheet material can be created. Previous work concentrated on forming fully developed bulges, i.e., at the end of the bulging process, both hinges of the bulge are in contact. This paper presents a numerical and experimental study aiming at optimizing the bulge shape to increase the bearable limit loads. Two new bulge designs are investigated, an ‘arrow bulge’ and a ‘wave bulge’. The paper details the results of FE-simulations of the bulge shapes under bending and torsion loads. Forming tools were designed and both bulge shapes were produced experimentally. The results show that the material flow under compressive plastic instability can be controlled and that the resulting bulge shapes yield improved strength in various load cases.

Metal forming often draws upon cutting or machining operations to produce the final part geometry. Both in sheet and in bulk metal forming, a large amount of scrap is produced by the limited capability of metal forming processes for net-shape production. Additive manufacturing, in contrast, enables the production of complex components with only little requirements for finishing operations. Its drawbacks, however, are the low productivity, the limited part size and the high energy consumption for powder production and melting during manufacturing. This paper explores the potential of combining metal forming and additive manufacturing to new process chains from the viewpoint of energy consumption. The production of load-adapted, locally reinforced sheet metal parts of Aluminium alloys is considered. The energy requirements for metal forming, additive manufacturing and the combination of both processes are compared. Powder production from primary and secondary Aluminium is regarded. 54 powder-producing companies were identified, 11 of which offer Aluminium powder material. So far, only a single company produces Aluminium powder from secondary Aluminium. It is shown that the process combination of metal forming and additive manufacturing may enable substantial energy savings for powder produced from secondary Aluminium.

Intermetallic Titanium Aluminides (TiAl) have been designed for high-temperature lightweight applications. Powder-bed additive manufacturing (AM) processes such as laser powder bed fusion (LPBF) or electron beam melting (EBM) allow near-net-shape production of TiAl components. However, TiAl parts produced by LPBF or EBM do not reach the structural integrity and mechanical properties of forged parts. The main post-processing step of TiAl parts made by AM is hot-isostatic pressing (HIP), which has several disadvantages such as a long process time and an undesired coarsening of the microstructure. High-performance TiAl components such as turbine blades are thus still produced by isothermal forging of preforms made by investment casting and hot isostatic pressing. Due to the low workability of TiAl alloys, often more than one deformation step is required, and the tooling costs and the low material yield make this process chain very expensive. This paper explores the feasibility of combining AM with isothermal forming in order to replace HIP by thermomechanical post-processing. The hot forming behavior of the Ti-43.5Al-4Nb-1Mo-0.1B (at. %) TNM-B1 alloy, manufactured by EBM and LPBF, is analyzed concerning the evolution of the voids and grain sizes and compared to hot isostatic pressing. It is shown that the fine microstructure produced by AM yields a much lower flow stress and faster globularization kinetics in comparison to conventional cast and HIPed material. While HIP experiments are shown to significantly coarsen the microstructure, isothermal hot working is shown to convert the AM microstructure to a dense and refined state. Moderate hot working with total strains of ∼1 of AM pre-forms may thus serve as an alternative process chain to conventional large strains forging of cast pre-forms and to AM + HIP in the series production of high-performance TiAl components.

As an alternative to joining by fusion welding, joining by upset bulging (JUB) can be applied in cases where tubes are joined to plates, sheet metal, or other tubes and profiles. If a tube is joined to a pierced flat plate, joining is accomplished by creating bulges in the tube by axial compression, which enclose and securely lock the plate. The JUB process has a large potential for reducing cycle times, realizing joints between different materials and for increasing the dimensional accuracy of the joints compared to fusion welding. The joints produced by this forming technique are free from the negative impact of heat affected zones on the material properties. However, the material undergoes large plastic deformation during the JUB process. When the bulges are fully compressed, local damage and failure can be observed which reduce the service life properties of the joints. This paper presents an experimental and numerical study of the damage evolution and crack initiation in mechanical joining by upset bulging. Experiments were carried out to analyse the occurrence of failure. The results are supported by FE analyses. Nucleation of cracks strongly depends on the final bulge height and consequently on the degree of deformation on the inner side of bulges. Tensile tests show that cracks in the bulge reduce the strength of the joint to half of the undamaged material. A new bulge design with a modified shape is presented, which reduces the damaging effect of the upset bulging process and thus improves the strength of the joints.

Metals 7(4), 113 (2017). doi:10.3390/met7040113, Published by MDPI, Basel

Kurzfassung Leichtbauteile aus umgeformten Magnesiumblechen lassen sich derzeit auf Grund der eingeschränkten Umformeigenschaften noch nicht wirtschaftlich herstellen. Um die Vorteile der wirkmedienbasierten Umformung auch bei der Umformung von Magnesiumblechen anwenden zu können, muss sie jedoch mit temperierten Werkzeugen und Wirkmedien erfolgen. In diesem Beitrag wird über die wirkmedienbasierte Warmumformung von Magnesiumblechen mit den beiden Verfahren Hochdruckblechumformung und hydromechanisches Tiefziehen berichtet. Dabei werden die Vorteile gegenüber dem konventionellen Tiefziehen ermittelt.