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The main objective of this work is to provide a basic understanding of the mechanisms and locations of defect formation during percussion laser drilling of microholes using ultrashort pulses. Through the application of high-speed synchrotron X-ray imaging, we have been able to observe the dynamic formation and evolution of these defects in real-time. Our findings indicate that the initial deviations in the borehole geometry are highly dependent on the applied laser fluence. Specifically, while higher peak fluences facilitate deeper drilling, there exists a critical threshold beyond which the position of these deviations begins to decrease as the fluence increases. This behavior can be partially predicted within a certain fluence range using an existing theoretical model, which our experimental observations have tested and validated. Consequently, this research not only advances our understanding of defect formation in laser drilling but also provides a predictive framework for optimizing drilling parameters to minimize defects and enhance borehole quality. [ABSTRACT FROM AUTHOR]

Laser beam welding (LBW), as a non‐contact process with short cycle times and small heat affected zone, is a key technology for automated metal fabrication. Despite its efficiency, the susceptibility of certain alloys to solidification cracks remains a significant challenge. These cracks emerge in the transition zone between liquid and solid phases during the solidification process. Thermo‐fluid dynamic processes within the melt pool play a crucial role in solidification crack formation during LBW, influencing heat distribution, mass transport, and consequently, the microstructure and mechanical properties of the weld. An in‐depth exploration of thermo‐fluid dynamics within the melt pool, contributes to an improved understanding of the correlations between process parameters and melt pool flow aiming to avoid solidification cracks. Therefore, in situ process investigations were conducted at beamline P07 of PETRA III at the German Electron and Synchrotron (DESY). 1.4404 stainless steel specimen containing an 5 wt.% of tungsten particles, serving as tracer, were additively manufactured using laser powder bed fusion. The tungsten particles are evenly distributed within the samples. High‐speed synchrotron x‐ray imaging of the process zone allowed for detailed in situ analyses. Leveraging the lower x‐ray absorption coefficients of the base steel material compared to tungsten, the particles appeared as dark dots in the images. The experimental setup involved blind welds on the samples, where a portion of the sample was melted by the laser beam, forming a molten pool in the center while the edges remained intact. The uniform distribution of the particles in the sample means that the movement of the particles in the molten pool is overlaid by static particles located in the unmelted edges of the sample. To enhance the observation and tracking of particle movement within the melt pool, the image contrast was optimized, and static particles were filtered out. The resulting images offer a visual representation of thermo‐fluid dynamical flows during LBW, based on the movement of tracer particles. Analysis was performed using an on Hessian blob detection and Kalman filter based tracking tool [1]. The results of this investigation provide valuable insights into the intricacies of thermo‐fluid dynamics during LBW, offering a foundation for the advancement of numerical modeling and simulation tools in the field of LBW. [ABSTRACT FROM AUTHOR]

The validation of laser welding of metallic materials is challenging due to its highly dynamic processes and limited accessibility to the weld. The measurement of process emissions and the processing laser beam are one way to record highly dynamic process phenomena. However, these recordings always take place via the surface of the weld. Phenomena on the inside are only implicitly recognizable in the data and require further processing. To increase the validity of the diagnostic process, the multispectral emission data are synchronized with synchrotron data consisting of in situ high-speed images based on phase contrast videography. The welding process is transilluminated by synchrotron radiation and recorded during execution, providing clear contrasts between solid, liquid, and gaseous material phases. Thus, dynamics of the vapor capillary and the formation of defects such as pores can be recorded with high spatial and temporal resolution of <5 μm and >5 kHz. In this paper, laser welding of copper Cu-ETP and CuSn6 is investigated at the Deutsches Elektronen-Synchrotron (DESY). The synchronization is achieved by leveraging a three-stage deep learning approach. A preprocessing Mask-R-CNN, dimensionality reduction PCA/Autoencoders, and a final LSTM/Transformer stage provide end-to-end defect detection capabilities. Integrated gradients allow for the extraction of correlations between defects and emission data. The novel approach of correlating image and sensor data increases the informative value of the sensor data. It aims to characterize welds based on the sensor data not only according to IO/NIO but also to provide a quantitative description of the defects in the weld. [ABSTRACT FROM AUTHOR]

Al-Si-Mg-based secondary cast alloys are attractive candidates for thin-walled high-pressure die castings for applications in the transport industry. The present study investigates the effect of manganese additions at high cooling rates on microstructure, mechanical properties, and on the dominating fracture mechanisms of alloy AlSi10Mg with an elevated iron concentration. Systematic variations of the Mn content from 0.20 to 0.85 wt pct at a constant Fe content of 0.55 wt pct illustrate the key changes in type, phase fraction, and shape of the Fe-containing intermetallic phases, and the corresponding influence on the alloy's ductility. For high-pressure die casting (HPDC), an optimal range of the Mn content between 0.40 and 0.60 wt pct, equivalent to a Mn/Fe ratio of approximately 1, has been identified. At these Mn and Fe contents, the high cooling rates obtained in HPDC result in the formation of fine and homogeneously distributed α-Al(Fe,Mn)Si phase, and crack initiation is transferred from AlFeSi intermetallics to eutectic silicon. The study interprets the microstructure-property relationship in the light of thermodynamic calculations which reveal a significant increase in undercooling of the α-Al(Fe,Mn)Si phase with increased Mn content. It concludes that the interdependence of the well-defined Mn/Fe ratio and the high cooling rate in HPDC can generate superior ductility in secondary AlSi10Mg cast alloys. [ABSTRACT FROM AUTHOR]