Inward solidification of cylinders: Reversal in the growth rate and microstructure evolution

The inward solidification of cylinders is investigated both numerically and experimentally. Experiments were performed with Pb–Sb hypoeutectic alloys having quite different freezing ranges. The present study aims to contribute to a better understanding about the correlation between a solidification thermal parameter (the growth rate) and the scale of the dendritic structure along the inward growth of cylindrical castings. It is shown, both by experimental results and numerical heat transfer simulations that the growth rate decreases from the casting surface, stabilizes along a range of positions in the casting and accelerates rapidly from 0.8 of the radius of the cylinder towards the center of the casting. It is also shown that the primary dendritic arm spacing accompanies the trend in the growth rate.