Grain impingement during solidification of cast iron

Simulations and experiments have been used to study the problem of grain impingement in cast iron. Calculation of the free surface in a volume which contains a large number of grains results in Avrami's relationship. Taking the average free surface of each individual grain gives higher values. Experimental measurements have been carried out in conditions similar to those of the second method. Results obtained by metallographic examination of quenched samples of spheroidal-graphite cast iron and uninoculated lamellar-graphite cast iron are in good agreement with the calculated results as obtained with the second method. This also confirms indirectly Avrami's relationship. Inoculated lamellar-graphite cast iron, however, shows higher values of the free surface during solidification due to the indented shape of the eutectic cells. The free surface relationship during dendrite solidification differs from the one of equiaxed grains and may be approximated by a simple model.