Due to differences in absorption coefficients and melting points, direct laser welding of dissimilar metals between copper and stainless steel(SS) remains a challenging topic.In this work, we present a blue-infrared hybrid laser welding technology for efficiently joining copper to SS. By leveraging copper's high absorption of the blue laser (455nm),preheats the material、improving absorption of IR laser and reducing welding defects caused by differences in absorption and heat dissipation. The high brightness of the IR laser ensures sufficient weld depth and joint strength.

The results demonstrate improved thermal management, leading to smoother welds and a reduction in defects, such as cracks and porosity, by optimizing key process parameters, such as laser power, welding speed, and offset.

Moreover, the technology was successfully extended to weld copper up to 19mm in thickness, illustrating the robustness and versatility of the hybrid laser welding technique for producing high-quality joints in challenging applications.

In recent years, there has been a growing focus on aluminium-copper welds, as substituting copper with aluminium can significantly reduce the weight and costs of electrical systems. Laser welding has emerged as a reliable and productive technology for joining dissimilar materials. However, welding of aluminium and copper often results in the formation of brittle intermetallic-compounds (IMCs), which also can exhibit higher electric resistance. A promising approach to minimizing IMCs involves the use of laser with wavelength ranging from 445 nm to 535 nm. Given that it is a diffusion-driven process, it promotes the formation of a dominant eutectic layer in the joint over intermetallic compounds. In this study, a blue laser source is employed for spot welding of copper and aluminium. The clamping pressure is varied from 0.25 N/mm² to 2.5 N/mm². The focus is on characterisation of the eutectic layer formed from Al2Cu and α-Al, together with IMCs.

E-mobility increasingly demands cost-efficient and lightweight solutions. Although copper remains indispensable in battery production for its excellent electrical and thermal conductivity, it is increasingly replaced with aluminum to reduce weight and production costs. However, complete substitution is challenged due to issues like contact erosion during operation, necessitating reliable copper-aluminum joints. Laser welding is preferred for its high precision, deep penetration, and minimal heat-affected zones. However, a major challenge in laser welding of copper-aluminum is the formation of brittle intermetallic compounds (IMCs) at the weld interface. This study investigates IMC formation mechanisms and the influence of cooling rates on their behavior in two laser welding processes: conventional and indirect laser welding. Indirect laser welding has recently been developed as a solid-state process to minimize material mixing and IMC formation, typical of fusion welding processes. This study includes a comparative analysis of the welding interface in both processes.

During fusion welding processes shielding gases are of major importance to protect the liquid metal from atmospheric contamination. These shielding gases play an important role in a number of aspects of welding, including the overall shape and microstructure of the weld, imperfections and the formation of weld bead and root. The aim of this work is to present the potential of an innovative and patented shielding gas nozzle which generates a spiral high-speed gas flow around the fusion zone and thus provides unidirectional welding conditions even at high welding speed > 10 m/min. Welding tests on butt and lap joints in stainless steel 1.4404 and titanium grade 5 show advantages with regard to uniform surface of weld bead and root. Furthermore, suppression of cracking and spattering can be observed, which result from the effective displacement of atmospheric gases by the spiral-shaped shielding gas flow.

A project associated to the authors aims to demonstrate an innovative liquid hydrogen tank concept for emission-free aviation. Liquid hydrogen tanks operate under a pressure of approximately 4 bar, resulting in "boil-off" gas—hydrogen that must be vented due to thermally induced pressure increases, which reduces efficiency. To minimize this, a multilayer vacuum insulation in a sandwich structure made of additively manufactured chromium-nickel steel is being developed. The individual segments of the resulting tank must be welded together. Laser beam welding in a vacuum combines the welding process and the creation of vacuum insulation in a single step. Trials with 2 mm thick stainless steel sheets, arranged at distances of 5–20 mm and welded together, demonstrate the process feasibility. The results show a broad parameter range for three-sheet connections, enabled by both beam oscillation and Brightline technology.

The cost aspect is becoming increasingly important in the manufacturing of complex additively manufactured components. One method of reducing costs is hybrid design, i.e. combining semi-finished products with the additively manufactured components. For this reason, the focus is on welding processes to improve overall performance of the final component. Laser welding is particularly suitable for joining components to avoid subsequent processes issues such as distortion due to the low heat input.

As part of the study, the aluminum alloys AlZn5.5MgCu (EN AW-7075) and AlSi7Mg0.6 (EN AC-42200) were used to build components using L-PBF and to weld them using laser high-frequency beam oscillation. That approach enables hot-crack free weld seams and provides high process stability towards avoidance of melt pool blow-outs. The paper shows the developed process approach and resulting properties (microstructure of the weld, tensile strength and fatigue strength) were compared with alternative welding processes (FSW, EBW and GTAW).