-Novel approach for reducing thinning during forming of foil metal MEERKAMP Max, UHLMANN Lars, MÜLLER Martina, HERRIG Tim, BERGS Thomas [button link="https:

Bipolar plates are key components of fuel cell systems, as they significantly determine efficiency, power density, and service life. In aerospace applications, their importance is further emphasized due to the dual requirement of corrosion resistance and strict weight reduction. Titanium Grade 1 combines low density and excellent corrosion resistance. However, its industrial application is limited by restricted formability. The aim of this paper is a systematic investigation of the forming behavior of Titanium Grade 1 foil material in order to define forming limits and derive manufacturing-oriented design recommendations for bipolar plates in aviation. Procedure. Sixteen distinct geometry features were developed to represent characteristic forming conditions. In addition to cross-section variations, the flow field angle was systematically altered to assess its influence on local stress and strain distribution. Furthermore, the key process parameters forming speed, forming force, and lubricant amount were varied to evaluate their impact on the forming quality. The assessment focused on form filling and material thinning. For this purpose, metallographic cross-sections were prepared, and optical 3D measurements were conducted using a Keyence system to precisely capture local wall thickness variations. Key findings Process parameters: The forming behavior of Titanium Grade 1 is strongly influenced by the applied forming force and lubrication. Form filling becomes sufficient only above 350 MPa (3.000 kN), while the lubricant amount is decisive for achievable forming depths due to the hydrostatic oil cushion effect. In contrast, forming speed shows no significant influence. Anisotropy remains a critical factor, particularly in 0° rolling direction, where premature thinning leads to fracture. Geometry parameters: Small radii are highly critical, while feature depth leads to expectedly higher thinning. Steeper flank angles improve form filling but at the cost of increased thinning. Pitch shows limited influence, although it may become relevant at very small values. Channel design is challenging, as sharp flow field angles consistently result in severe thinning and pose difficulties in tool manufacturing.

Additive manufacturing (AM) enables rapid, near-net-shape fabrication with high material efficiency, but the resulting components often exhibit surface roughness, microstructural heterogeneity, and tensile residual stresses that reduce their performance. Machine hammer peening (MHP) is a mechanical surface treatment capable of modifying the surface integrity of AM components. It can be applied either as a conventional post-processing step after fabrication or as a hybrid interlayer treatment integrated into the build process. In this study, the effects of MHP process parameters and treatment strategies on wire-based laser metal deposition (LMD-w) Inconel 718 components were investigated, including the implementation of hybrid interlayer MHP. Surface topography, hardness, microstructure, and residual stresses were examined experimentally, while numerical simulations were developed to support the measurements and to characterize local contact conditions and plastic strain evolution during peening. The results show that MHP significantly reduces surface waviness and roughness, increases near-surface hardness, refines the microstructure, and introduces deep compressive residual stresses. Furthermore, hybrid interlayer MHP enhances the depth and uniformity of the modified layer by influencing the evolving microstructure during deposition. Standard forged Inconel 718 samples were also treated with MHP as a reference, showing comparable characteristics between the forged and AM components. These findings demonstrate that MHP is a versatile and effective modification technique for improving the performance and reliability of AM components, particularly when implemented as a hybrid interlayer treatment during the AM process.

Die Herstellung von rotationssymmetrischen Crimpkontakten für Rundsteckverbinder muss ökologische Nachhaltigkeit und hohe Produktivität vereinen. Im Vergleich zur derzeit eingesetzten Zerspanung von Rundsteckverbindern ermöglicht das Kaltfließpressen eine nahezu vollständige Werkstoffausnutzung und reduziert den CO₂-Fußabdruck erheblich. Dieser Beitrag zeigt Potenziale, Herausforderungen und Entwicklungsbedarfe bei der Umstellung von zerspanender auf kaltfließpressende Fertigung auf.