Abstract
The relation between eutectic cell number Ne (number/cm2) and cooling rate (°C/hr) or solidification rate V (cm/hr) is represented by the following equation. Ne = A·Rm, Ne = B·Vn, where A, B, m and n are constants. The relation between graphite spacing in eutectic cell λe(μm) and R or V is represented by the following equation. λe = C·Rk, λe = D·Vl, where C, D, k and l are constants (k, l<0). But the relation of λe−R or λe−V was not the extension of λp−R or λp−V relation in the lamellar structure, where λp is graphite spacing in lamellar structure. Whenever eutectic cells were observed, there were austenitic dendrites in the specimen. Eutectic cells formed in line around the axis of austenitic dendrite. Graphite in a eutectic cell was three-dimensionally continuous. Graphite was intermeshed at the colony boundary but graphite was free at the eutectic cell boundary. There was a sub-boundary, which was characteristic of a colony boundary in the eutectic cell. It was assumed from the calculation of wettability that austenitic dendrite could not be the nucleation site of graphite, while graphite could be the site for austenite. Undercooled graphite which generated in a colony or in a eutectic cell, was considered to be a cooperative growth.
