Numerical Simulation of Macrosegregation During Vertical Solidification

摘要

A continuum formulation based mathematical model has been employed to analyze the evolution of thermosolutal convection, isotherms, liquid fraction profiles and macrosegregation profiles during vertical solidification of lead-rich binary lead-tin alloys. The initial conditions, boundary conditions and microstructural parameters of this model have been taken from controlled experiments performed on lead-tin system. Numerical simulations were carried out for three chosen experiments on Pb-35 wt pet. Sn alloy with different cooling rates. The convection was very weak in case of vertical solidification. It was also observed that the nature of the flow field did not show significant effect on thermal field. However, there was substantial effect of nature of flow on macrosegregation. It was found that the choice of permeability model, especially near the liquidus, played a significant role in the evolution of macrosegregation during vertical solidification. Through the use of appropriate permeability model, the predicted profile of average macrosegregation in ingots along the vertical (i.e., axial) direction showed reasonable agreement with experimental data over a wide range of cooling rates.