A SIMPLE ANALYSIS OF THE EFFECT OF CONVECTION ON THE STRUCTURE OF THEMUSHY 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 net work by thermoelectric magnetohydrodynamic (TEMHD) effect. We study he re the influence of convection on the mushy zone during the horizontal directional solidification of a CuAg 60% mass and an AlCu 10% mass al loy. It is found that the spacing between the primary dendrite arms in creases drastically when a diffusive solute transport regime is approa ched while, in a well-established convective regime, it is weakly infl uenced by an increase of the Bow intensity. A criterion relating spaci ng to convection is proposed. A simple modelling is then derived and t he effect of convection on liquid fraction, size of the freckle and pr imary spacing in the mushy zone is quantified, assuming a 2D crucible and parallel flow. (C) 1998 Elsevier Science B.V. All rights reserved.