Fig. 1. (a) Primary and secondary melt flow in the unidirectionally solidified sample, (b) simulated secondary flow in the pure liquid phase [18], (c) simulated “Christmas Tree Like” (CTL) microstructure [18], (d) mechanism of columnar/equiaxed transition (CET) induced by fragmentation of the dendrites.

Fig. 2. Sketch of the solidification facility. 1: Sample, 2: alumina capsule, 3: quartz tube, 4: copper cooling core, 5: furnace with four heating zones, 6: step motor, 7: RMF inductor, 8: water cooling, 9: basement.

Fig. 3. The magnetic induction at 10 mT (a) vs length of the inductor and (b) on an arbitrary plane vs the angle.

Fig. 4. The experimental set-up

Fig. 5. The grain structure of the sample with the measuring spots (white lines): (a) first non-stirred part, (b) first transient zone (CET), (c) stirred part, (d) second transient zone (ECT) and second non-stirred part.

Fig. 6. Grain structure on the parallel section of the sample at different areas: (a) first transient zone, (b) stirred part, (c) second transient zone, (d) second non stirred part.

Fig. 7. The “Christmas Tree-Like” (CTL) structure.

Fig. 8. Grain structure: (a) first non-stirred part, (b) stirred part and dendritic structure, (c) first non-stirred part, (d) stirred part on the cross-section.

Fig. 9. Ratio of the length to the width of grains in three different parts of the sample.

Fig. 10. The measured amount of eutectic: (a) first non-stirred part, (d) stirred part, the calculated Si concentration, (b) first non-stirred part, (e) stirred part, the SDAS, (c) first non-stirred part, (f) stirred part.

Fig. 11. Measured Si concentration by EDS: (a) stirring is on, (b) stirring is off.

Fig. 12. (a) Average amount of eutectic along the sample axis, (b) average Si concentration along the sample axis.