Welding Making the invisible visible

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Researchers from Fraunhofer ILT and RWTH Aachen—Chair for Laser Technology (Germany) have managed to observe welding processes in more detail than ever before using synchrotron radiation: making vapor capillaries, melt movements, and defects visible.

In the interdisciplinary Laser Meets Synchrotron Team at the German Electron Synchrotron (DESY) in Hamburg, the Fraunhofer Institute for Laser Technology ILT and the RWTH Aachen—Chair for Laser Technology are researching fundamental scientific questions that lead to industrial innovations. Project leader Christoph Spurk from RWTH Aachen (Germany) coordinates the transport and setup of the systems, lasers, and optical components, and assigns tasks to specialists from the fields of physics, IT, materials science, and mechanical engineering. The research team delves into industrial laser processes such as welding, drilling, and cutting with the aim of better understanding material properties and behavior and eventually optimizing processes. "With the synchrotron radiation at DESY, we can visualize realistic laser processes in real-time, observe vapor capillaries, melt movements, or the formation of pores," explains Spurk.

Optimized Laser Processes for Industry and Research

The research results show that if the laser settings are adjusted, stress cracks are significantly reduced, porosity is minimized, and electrical conductivity can be increased. Vapor capillaries and melt movements, which often lead to defects, were visualized in high resolution for the first time, enabling the optimization of welding processes for high-performance batteries.

With their outstanding brilliance and intensity, synchrotron radiation enables investigations with a resolution in the micro- and even nanometer range, providing insights into the finest material structures and dynamic processes. Optical systems specifically focus the laser radiation on the materials; high-speed cameras are used for visualization, achieving frame rates of up to 50,000 frames per second—Spurk and his team are already working on a system that will reach 200,000 Hz in the future.

To visualize the phase contrast, the team uses scintillators that convert X-ray radiation into visible light. If the contrast is still too low, the researchers add tungsten or tungsten carbide particles to the material. The particles appear as black dots in the images and provide insights into the melt movement.

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Real-Time Visualization Identifies the Smallest Material Defects

In the automotive sector, aerospace, hydrogen technology, or microelectronics, for example, flawless welding of copper or aluminum connections is essential, as is the case for metal and plastic connections. Only through real-time visualization can the smallest material defects be identified, which would not be visible with conventional methods.

"The investigation of complex material combinations such as copper-aluminum connections is extremely important for electromobility, where they are used in high-performance batteries and other critical components," explains Dr. Alexander Olowinsky, head of the Joining and Cutting department at Fraunhofer ILT. "Thanks to the data obtained at DESY, such connections can be manufactured with higher strength and reliability. In the field of lightweight construction, we are also examining other structuring processes, and the results flow directly into the development of new technologies."

Synchrotron radiation allows for the early detection of stress cracks and unwanted structures in aluminum-titanium connections in the aerospace industry, optimizing the manufacturing process. Additionally, laser powder welding of nickel-based superalloys, such as for turbine blades, is improved with the help of high-speed recordings. In microelectronics, highly precise joining processes are essential. Analyzing melt movements in ultrathin copper tracks helps to prevent short circuits and material fatigue, which is particularly important for the production of semiconductors and printed circuit boards.

Our strength lies not only in conducting these experiments but also in understanding and interpreting the results, processing the complex data, and making it usable.

Christoph Spurk

From Big Data to Smart Data: Precise Analyses for Industrial Innovations

The expertise of the Laser Meets Synchrotron partners plays a key role in the use of this technology. The data obtained requires specialized analyses that are only possible with solid know-how and dedicated software—the research team returns to the institutes with up to 50 terabytes of data.

"Our strength lies not only in conducting these experiments but especially in understanding and interpreting the results, preparing the complex data, and making it usable," explains Christoph Spurk. "We turn Big Data into Smart Data." This is only possible with the team's interdisciplinary approach; only in this way can the data obtained at the synchrotron be transferred into practice.

The economic benefit for customers and partners goes far beyond process optimizations: The data and insights gained form the basis for entirely new business models, such as in the field of data-driven material development. With the precise analysis results, companies can develop custom materials for specific applications, giving them a decisive competitive advantage. Companies like Audi, Bosch Research, and Denso have been able to make their production processes more efficient and shorten development cycles through the collaboration.

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