Influence of permeability on the grain refinement induced by forced convection in copper-base alloys

Comparative study of the influence of natural convection on directional solidification of Al–3.5wt% Ni and Al–7wt% Si alloys

“…Dedicated careful experimental studies in the microgravity environment of space are needed, in order to further clarify the mechanism of fragmentation by suppressing the effects of buoyancy. Conversely, fragmentation induced by convection in the mushy zone should be characterized during directional solidification on earth (Flemings, 2000;Beckermann, 2002;Campanella et al, 2003). Furthermore, it should be pointed out that fragmentation is a microscale phenomenon whereas the interaction of interdendritic flow with dissolution and remelting process has to be considered in a complete global model.…”

“…An important deduction of LSRE is that solute-rich melt will cause local dissolution (or remelting) of dendrites, when flow velocity is in the direction of increasing temperature and larger than isotherm velocity, in the reference frame of the crucible (Beckermann, 2002). When dendrite fragments formed by this local dissolution mechanism are carried into the bulk melt, they could promote columnar to equiaxed transition (CET) where local undercooling condition is favorable (Hellawell et al, 1997;Campanella et al, 2003;Spittle, 2006 A classical approach of solidification modelling is to treat the liquid and mushy regions in separate domains. The fluid motion in the melt region is modelled in general by the Navier-Stokes equations, while that within the mushy is modelled as in a porous medium (Darcy's law).…”

Effect of Coil Design on the Temperature and Velocity Fields during Solidification in Electromagnetic Stirring Processes

“…Also, the interaction between the induced current and the applied magnetic field produces EM forces, which drive the flow in the melt. The flow behavior in EM stirred melts is generally controlled by the applied magnetic field used, namely stationary, 2,7,8) rotating, 9) or traveling magnetic fields. 5,10) Moreover, the resulting flow field is highly sensitive to variations in coil design, namely the coil configuration 11,12) and the location of the coil with respect to the melt.…”

“…There are essentially two types of flow models for the mushy region, namely single-zone 7,21,22) and dual-zone models. 23,24) The single-zone model treats the entire twophase region as a porous medium, with the flow being damped via Darcy's law.…”

“…The dual-zone model divides the mushy region into two domains: (i) the suspended particle region, and (ii) the fixed particle region, with the transition between regions occurring at the coherency point. In modeling EM solidification processes, the former model was used by Rappaz and coworkers 7) and Prescott and Incropera, 22) while the latter was used by Pardeshi et al 24) In each of these studies, an approximate analytical solution was used to describe the EM force field in the system. This limits the capability of these models to address the role of the coil design on the solidification behavior.…”