GRAPHITE GROWTH IN CAST IRON.

Ductile cast irons containing additions of Mg or Ce will produce sessile drops with shapes that reflect the energy of the substrate on which they are melted. Gray irons containing contaminants such as S and An tended, instead of reflecting the energy of the substrate, to wet or spread on the high-energy prism graphite substrates. The reason for the wetting is the adsorption of the surface-active contaminants at the prism plane-melt interface. This adsorption is a key in understanding the growth of graphite during cast iron solidification. The mechanism of solidification of gray and ductile iron may be explained in terms of interfacial energy and adsorption, in a way slightly different from previous explanations.