Laser welding in e-mobility presents significant challenges, particularly for copper and aluminum joints, due to their high reflectivity, thermal conductivity, and susceptibility to defects like porosity or cracking. Optimizing the energy distribution within the laser beam is key to stabilizing the melt pool and improving weld quality.

We introduce a unique beam-shaping solution that generates a four-spot pattern to enhance aluminum battery pack welding. This approach is implemented on a universal platform compatible with all laser sources. Various four-spot configurations will be analyzed, with welding performance systematically compared to the unshaped beam.

Laser beam welding is a very efficient process for joining two copper hairpins in electric drives, known as hairpins. The occurrence of welding defects reduces the quality of the weld. Pores, for example, reduce the conductive cross-sectional area, which increases the electrical resistance and further impairs the strength of the connection. In addition, complex testing procedures as for example computational analyses must be used to ensure that each individual weld meets the quality criteria. This is why this work focuses on in- process measurements to detect defects, such as pores. For the investigation optical coherence tomography was used to investigate in the detection of welding defects during the welding of these hairpins. Computational analyses (CT) and high-speed videos were used to determine the context of the optical coherence tomography signal and the weld result. It was found that optical coherence tomography is a good method to determine defects real-time capable.

Demand for precise measurements of high-speed laser welding depth is increasing due to growing e-mobility applications. Optical coherence tomography (OCT) can measure keyhole depth in real time. Newer fiber laser generations, ideal for such applications, offer single mode core/ring configurations. However, OCT’s usability with small keyhole apertures may cause measurement inconsistencies. This work proposes a systematic analysis of signal behavior using a contemporary fiber laser with a single mode core and a ring with separate power control, producing focal core and ring sizes of 40 µm and 285 µm, respectively. Bead-on-plate experiments were conducted on 5 mm thick EN AW-1050 Al-alloy. Core and ring power levels were systematically analyzed along with scan speeds. The OCT focal beam of 35 µm was aligned with the laser beam for different scan speeds. Keyhole depth was compared to molten seam depth from metallographic cross-sections. Feasibility windows for stable OCT measurements were identified.

Optical coherence tomography (OCT) can be used to determine the depth of the keyhole during laser deep penetration welding. However, due to the nature of the OCT data a statistical evaluation approach is necessary, reducing the possible temporal resolution. At the same time, keyhole welding is a strongly dynamic process and the penetration depth of welds can fluctuate even under constant process parameters. In this study the time scales on which weld penetration depth deviations can be detected are investigated by examining longitudinal cross sections of weld seams and comparing to the corresponding OCT measurements. Differences between the Materials Steel (S235JRC), Aluminum (EN AW-5083) and Copper (Cu-ETP) are examined. Results show that OCT measurement frequencies are high enough for spontaneous weld depth deviations to be recognized with sufficient precision. Thus, controlling the laser power to achieve a more uniform weld depth driven by real-time OCT measurements is a plausible approach.

Sustainability is becoming increasingly important in production of vehicles. The e-mobility transition has shifted the CO2 footprint from use to production phase, where secondary alu-minum alloys in structural castings are known to offer significant CO2 reduction potential. However, accumulation of copper, iron and zinc and the hydrogen content in the melt pose major challenges for casting and subsequent joining processes. In laser welding, dynamic modulation of intensity distributions in the weld pool can overcome the latter issue. In experi-mental studies covering high pressure die cast AlSi10MnMg alloys with secondary material content levels ranging from 0 wt.-% to 89 wt.-%, castability and weldability were investigated and the structural and mechanical properties of the joint determined. The results contribute to the optimization of sustainable car body production methods, providing a path towards cost-effective differential lightweight design solutions as economically, technologically and ecologi-cally competitive alternatives to large-scale casting technologies (giga-casting).