Experimental and numerical investigation on mass transfer induced by electromagnetic field in cold crucible used for directional solidification

Abstract

Electromagnetic stirring induced by alternating magnetic fields could generate complex mass transfer in the liquid metals. In this paper, the flow field and the mass transfer behavior induced by the high frequency magnetic field in a square electromagnetic cold crucible (EMCC) used for directional solidification was experimentally and numerically investigated. By using tungsten particles as the tracer, the experiments under different operating powers and times were carried out, and the distribution of the particles in melt after cooling were analyzed. The results show that two mean eddies exist in the half meridian plane of the molten pool, and the skin effect results in a stronger convection within the skin layer. The mass moves following the mean eddies and emerges preferentially in the skin layer; when the mass is transported to the region between the upper and the lower eddies, which is homogenized in axial by the strong oscillations of convection. However, there is a concentration gradient along the radial in melt due to the skin effect. It found that the mass distributes more uniform with higher operating power or longer time. Moreover, the inhomogeneous convection at the vicinity of solid-liquid interface leads to the heterogeneous distribution of the mass, which aggravates the deflection of solid-liquid interface and changes the phase transition path during crystal growth.