The possible formation of graphite eutectic grains in the center of a casting was confirmed by computer simulation. Accordingly, the development of fine-grained zones can be explained by an increase in the degree of undercooling toward the end of solidification. Nevertheless, the computer simulation predictions indicated that an increase in undercooling, alone, is not sufficient to account for the development of a fine-grained central zone. Both the area of the fine-grained zone and the number of grains are found to depend on factors such as the shape and type of the sand mold, and on the casting temperature. In particular, good agreement is found between the predicted area of the fine-grained zone and the grain distribution at the cross section of a cylindrical casting, when compared with the experimental outcome.
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