A simple analysis of the effect of convection on the structure of the mushy zone in the case of horizontal Bridgman solidification - Comparison with experimental results

A magnetic field is used to modify the fluid flow in the dendritic network by thermoelectric magnetohydrodynamic (TEMHD) effect. We study here the influence of convection on the mushy zone during the horizontal directional solidification of a CuAg 60% mass and an AlCu 10% mass alloy. It is found that the spacing between the primary dendrite arms increases drastically when a diffusive solute transport regime is approached while, in a well-established convective regime, it is weakly influenced by an increase of the Bow intensity. A criterion relating spacing to convection is proposed. A simple modelling is then derived and the effect of convection on liquid fraction, size of the freckle and primary spacing in the mushy zone is quantified, assuming a 2D crucible and parallel flow. (C) 1998 Elsevier Science B.V. All rights reserved.