Investigation of ultrashort pulse laser material processing of low- and high-entropy alloys using an ultrafast temperature and density sensor

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Laser materials processing is currently the most common application for modern laser systems, followed by telecommunications, medicine, and basic research. Especially the freely designable processing of materials with a variety of manufacturing processes has made the laser an indispensable flexible tool. Because of its high precision and broad range of applications, ultrashort pulse laser material processing of metals and their alloys has enormous potential for Industry 4.0. The optimization of process parameters in terms of quality, energy and resource efficiency is crucial. However, due to widely varying material properties and laser system parameters, no universal process window has been developed so far. Particularly for novel alloys such as high-entropy alloys, which are becoming progressively important due to rising technical demands. The project's goal is to investigate a quantitative, experimentally validated model of ultrashort pulse laser material processing of various iron and nickel-containing alloys of 3d transition metals, ranging from conventional stainless steels to modern high-entropy alloys. As a result, a thorough understanding of the process dynamics will be developed through the use of an experimentally validated model. This can solely be accomplished through the close interplay of theory and experiments. Utilizing ultrafast time-resolved ellipsometric and interferometric pump-probe experiments, as well as theoretical ab-initio modeling, will allow quantitative conclusions on the transient change of thermodynamic state variables to be drawn. The experimentally validated model should be able to predict both time-dependent observables like transient reflection, absorption, and surface bulging as well as final state observables like ablation thresholds and efficiencies. The developed methodology, referred to as an "ultrafast temperature and density sensor” and the resulting findings are expected to contribute significantly to the overall quantitative understanding of ultrashort pulse laser material processing of modern alloys. Furthermore, novel insights into the material parameters of these alloys in exotic states, which have previously been unexplored, are expected.