Spatially tailored laser energy distribution using innovative optics for gas-tight welding of casted and wrought aluminum alloys in e-mobility

Electric mobility is undergoing a very rapid maturation process [A. Kampker, K. Kreisköther, P. Treichel, T. Möller, Y. Boelsen, and D. Neb, “Electromobility trends and challenges of future mass production,” in Handbook Industry 4.0, edited by W. Frenz (Springer, Berlin, 2022), D. Ziegler and N. Abdelkafi, “Business models for electric vehicles: Literature review and key insights,” J. Cleaner Prod. 330, 129803 (2022)]. While conventional vehicle design disciplines such as car body design are established, electromobility-specific disciplines are in the technological orientation and ramp-up phase. In particular, the demand for components like batteries, e-motors, and power electronics is growing continuously [A. Kampker, K. Kreisköther, P. Treichel, T. Möller, Y. Boelsen, and D. Neb, “Electromobility trends and challenges of future mass production,” in Handbook Industry 4.0, edited by W. Frenz (Springer, Berlin, 2022), D. Ziegler and N. Abdelkafi, “Business models for electric vehicles: Literature review and key insights,” J. Cleaner Prod. 330, 129803 (2022)]. One of the major materials chosen for these parts is aluminum alloys [C. Prieto, E. Vaamonde, D. Diego-Vallejo, J. Jimenez, B. Urbach, Y. Vidne, and E. Shekel, “Dynamic laser beam shaping for laser aluminium welding in e-mobility applications,” Procedia CIRP. 94, 596–600 (2020)]. Next to the material-specific challenges and mentioned requirements, the focus is on the gas-tight welding of aluminum alloys for parts like casted power electronics housings and heat exchangers made of sheet metal or extrusion profiles. Gas-tightness is a requirement, on the one hand, to shield electronic components from the influence of the surrounding environment and, on the other hand, to prevent leakage of the water-cooling circuit [C. Prieto, E. Vaamonde, D. Diego-Vallejo, J. Jimenez, B. Urbach, Y. Vidne, and E. Shekel, “Dynamic laser beam shaping for laser aluminium welding in e-mobility applications,” Procedia CIRP. 94, 596–600 (2020), A. Artinov, M. Bachmann, X. Meng, V. Karkhin, and M. Rethmeier, “On the relationship between the bulge effect and the hot cracking formation during deep penetration laser beam welding,” Procedia CIRP 94, 5–10 (2020)]. This paper offers insight into the requirements of these parts and an innovative optics approach with a novel MultiFocus solution. Material-specific challenges (e. g. porosity), especially, for helium-tight welding of aluminum casted housings with forging alloys are characterized. This analysis is conducted using gas-tightness measurements, CT-scans, micrographs, and high-speed recordings in order to elaborate on the fundamental laser-material-process interdependencies and the correlation between the process and resulting quality, in terms of tightness. Furthermore, high-speed synchrotron recordings are conducted at the DESY and based on that, a detailed evaluation of laser and material interaction is conducted. This allows an explanation of the interactions for the prevention of pore formation in aluminum alloys and, thus, the characterization of the boundary conditions for a reliable process of gas-tight welding on aluminum alloys [C. Prieto, E. Vaamonde, D. Diego-Vallejo, J. Jimenez, B. Urbach, Y. Vidne, and E. Shekel, “Dynamic laser beam shaping for laser aluminium welding in e-mobility applications,” Procedia CIRP. 94, 596–600 (2020)]

The interactions of bacteria with fungi in soil:Emerging concepts

In this chapter, we review the existing literature on bacterial fungal interactions in soil, exploring the role fungi may play for soil bacteria as providers of hospitable niches. A focus is placed on the mycosphere, i.e., the narrow zone of influence of fungal hyphae on the external soil milieu, in which hypha-associated bacterial cells dwell. Evidence is brought forward for the contention that the hyphae of both mycorrhizal and saprotrophic fungi serve as providers of ecological opportunities in a grossly carbon-limited soil, as a result of their release of carbonaceous compounds next to the provision of a colonizable surface. Soil bacteria of particular nature are postulated to have adapted to such selection pressures, evolving to the extent that they acquired capabilities that allow them to thrive in the novel habitat created by the emerging fungal hyphae. The mechanisms involved in the interactions and the modes of genetic adaptation of the mycosphere dwellers are discussed, with an emphasis on one key mycosphere-adapted bacterium, Burkholderia terrae BS001. In this discussion, we interrogate the positive interactions between soil fungi and bacteria, and refrain from considering negative interactions.</p