cfaed Seminar Series

Abstract

Solidification processes extend over a length scale range of about 9 decades, starting from the scale of the casting mold, over the formation of the dendritic microstructure towards the attachment kinetics at the nano-scale. In the talk, processes on three different length scales are considered. In the first part, an overview is given on the works at HZDR conducted on electromagnetic flow control at the macroscale O(10-1 m). In particular it is demonstrated how a forced convection, generated by Lorentz forces in modulated magnetic fields, can be used for a reduction of undesired macrosegregation.
The second part covers in-situ X-ray visualization experiments of solidification. Using microfocus tubes, both the interplay between forced and natural convection and the formation of freckles is shown. Furthermore, pinch-off of secondary sidearms of dendrites is revealed in recent synchrotron experiments. The simulation of pinch-off events by means of phase-field simulations is discussed in the third part. Based on recent simulations, a general equation is developed for the specific interfacial area evolution that maps most of the previously performed synchrotron X-ray tomography and isothermal coarsening experiments.