Evolution of Solid–Liquid Interface Influenced by Fluid Flow During Transverse Static Magnetic Field-Electric Current-Assisted Directional Solidification

The evolution of the solid–liquid interface (SLI) during directional solidification under the flows induced by both a transverse static magnetic field (TSMF) and the simultaneous application of TSMF and direct current (DC) was investigated experimentally and numerically. The results revealed that the SLI inclination initially increased and then decreased, ultimately forming a slightly sloping SLI as the TSMF increased from 0 to 1 T under case of Al–15Sn–1Cu alloys in the 3 mm crucible. However, in the case of Cu–15Ni–8Sn alloys in a 10 mm crucible, a severely sloping SLI was observed at 6 mT. As the TSMF increased to 0.8 T, the SLI gradually transformed to a slightly slope on the left side and became planar in the middle and on the right side. The numerical results indicated that the flow increased with both the TSMF (0–1 T) and the crucible size. The flow-induced variations in temperature and solute distribution were found to be responsible for the SLI evolution. Moreover, the application of a vertically downward DC decreased and ultimately reversed the SLI inclination under TSMF, as the DC-induced Lorentz force distribution opposed the thermoelectric magnetic force distribution. Conversely, the vertically upward applied DC generated a driving force in the same direction as the thermoelectric magnetic force, thereby strengthening fluid flow and resulting in a slightly sloping SLI and the appearance of freckles.