Application of neutron radiography for in-situ visualization of gallium solidification in travelling magnetic field

D. Musaeva^{1, 2} - E. Baake¹ - A. Köppen¹ - P. Vontobel³

¹ Leibniz University of Hannover, Wilhelm-Busch Str. 4, 30167 Hannover, Germany
² Kazan State Power Engineering University, 51 Krasnoselskaya, 420066 Kazan, Russia
³ Paul Scherrer Institute, PSI, CH-5232 Villigen, Switzerland

Abstract
Visual information about the influence of electromagnetic stirring on solidifying metal is essential for the optimization of material processing methods. It has recently been shown that the method of neutron radiography can be extended for the investigation of complex metallurgical processes in opaque media. The paper discusses the results of successful neutron imaging technique application to observe in real time the formation of the solid/liquid interface of a solidifying gallium melt stirred by a travelling magnetic field. Continuous and pulsed at low frequency application of the field was investigated to analyze the influence of the EM driven flow on the formation of ingots. The shape of the interface between the solid and liquid phases and the structural irregularity of the solid/liquid surface were analyzed. The results were compared with those for crystal growth without electromagnetic stirring. Comparing to other regimes has shown that the pulsed stirring at frequencies close to the characteristic frequency of melt circulation leads to the formation of a flatter solidification front with a more regular solid/liquid interface, which evidences of more uniform heat transfer conditions in the melt, and the method of neutron radiography makes it possible to obtain such information. Tables 1, Figs 6, Refs 17.