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)].

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It is shown that a temporal modulation of the laser power can prevent the formation of hot cracks during deep-penetration laser welding of tempered steel. For this purpose, the influence of the modulated laser power on the cumulated length of the hot cracks in the weld seams was quantified. Varying amplitude and frequency of the modulation significantly changes the pattern and length of the hot cracks. Moreover, hot cracks can be prevented entirely in a specific range of the modulation frequency that depends on the welding speed. Our results indicate that the reduction of hot cracks might be related to a change of the fluctuating length of the weld pool, which was detected by means of thermographic imaging.