Numerical simulation and fourier thermal analysis of solidification kinetics in high-carbon Fe-C alloys

Abstract

The aim of this work was to carry out both experimental and numerical simulations of cast iron solidification under various conditions. The experimental work was based on a novel technique of thermal analysis known as the Fourier method, whereas solidification modeling was possible by solving the Fourier equation with a heat source. Moreover, a comparison between the Fourier and the Newtonian method indicated that their predictions are appreciably different. The Newtonian method is rather insensitive to the actual thermal gradients and predicts a clear maximum in heat generation at the onset of solidification. In contrast, the Fourier method incorporates the effect of actual thermal gradients and predicts two successive heat generation peaks of increasing magnitude as solidification proceeds. In particular, it was found that the experimental outcome of solidified volume fractions agrees closely with the predictions of the Fourier method. In this case, both experimental and computer simulations on 30- and 40-mm-diameter cylindrical specimens indicated that the solidified fraction followed a sinusoidal trend. Moreover, it was found that under normal solidification conditions, secondary nucleation of fine grains can occur near the center of a cylindrical cast iron specimen. Secondary grain nucleation is attributed to the development of a second under-cooling maximum which easily exceeds the initial one. Finally, the effects of inoculation were investigated in plain cast iron and as a function of the inoculation time. Accordingly, in all cases, the computer simulations were in close agreement with the experimental outcome.