Temporally and spatially highly resolved reconstruction of vapor capillary geometry during laser beam welding using synchrotron radiation

Welds of electrical components made of aluminium and copper need high electrical and mechanical quality. Process instabilities do not allow a continuous reproducibility. To generate a deeper understanding of the process and to evaluate process dynamics, it is possible to use modern in situ analysis methods. In this work, in situ phase-contrast high-speed videography using synchrotron radiation is presented. The phase contrast method reveals the phase boundaries between solid, liquid, and gaseous phases. A spatial resolution down to < 20 mm is possible due to the high coherence of the synchrotron beam, which allows to observe small vapor capillaries of fiber lasers with < 100 mm diameter. 3D capillary geometries are reconstructed from 2D image data of welds on aluminium using a fibre laser and disc laser. Ray tracing is performed using this reconstruction, which allows the time resolved tracking of the laser beam inside the vapor capillary for quantitative estimations.