Fig. 1. Schematic illustration of synchrotron radiation imaging experimental setup.

Fig. 2. Synchrotron X-ray radiograph showing the evolution of microstructure: (a) grey image after image processing and (b) false-color image.

Fig. 3. Sequences of synchrotron X-ray radiographs showing time evolution of equiaxed growth of the Sn-50 wt.%Pb sample for the four solidification experiments: (a) j = 0 A/mm2; (b) j = 1 A/mm2; (c) j = 1.5 A/mm2; (d) j = 1.8 A/mm2. t = 0 s represents the time when cooling is applied.

Fig. 4. Microstructures of Sn-50 wt.%Pb alloy at the end of solidification (180 °C, t = 3000 s) showing the effect of DC on grain refinement: (a) j = 0 A/mm2; (b) j = 1 A/mm2; (c) j = 1.5 A/mm2; (d) j = 1.8 A/mm2; (e) grain size as a function of DC density.

Fig. 5. Variation of the nucleated grains number in the four experiments. t = 0 s represents the time when cooling is applied.

Fig. 6. Time variation in the growth rate of the equiaxed dendrites with different DC density for Sn-50 wt.%Pb alloy. t = 0 s represents the time when cooling is applied.

Fig. 7. Synchrotron X-ray radiographs showing the effect of DC on dendrite morphology: (a) Sn-50 wt.%Pb alloy solidifying without DC; (b) Sn-50 wt.%Pb alloy solidifying with DC; (c) Sn-12 wt.%Bi alloy solidifying without DC; (d) Sn-12 wt.%Bi alloy solidifying with DC.