Sensitivity of Thermophysical Material Properties on Solidification Simulation of Al-Si Binary Alloys

The challenges in the numerical simulation of the solidification of binary alloys are not only in the complexity of the algorithms themselves, but also in the validity of the data used to define the material properties of the various phases to obtain a valid simulation. The effect of material properties on the numerical simulations was investigated in the present study wherein the Al-3 wt pct Si hypoeutectic binary alloy was solidified such that the solidification front traveled against the gravity vector (upward solidification). Numerical simulations were carried out with a new algorithm that was developed to include the effect of undercooling of the liquid temperature prior to the solidification event. The effect of specific heat of solid, density of solid, solute diffusivity coefficient of liquid, and thermal conductivity of solid on transient temperature distribution and solidification start time at mushy zone/liquid interface was investigated. It was found that specific heat and thermal conductivity of the solid could not be assumed as constants, whereas most properties in the liquid phase could be assumed as constants for the temperature range used in the study and the experiments used for validation (low initial melt superheat temperature). These properties were enumerated and quantified. The results of the numerical simulations using the optimum set of material properties were validated by experiments.