A Newly Observed Pattern of Imperfect Graphite Spherulite in Nodular Iron

抄録

In a previous paper the present author showed several patterns of imperfect graphite spherulite appearing in nodular iron improperly treated with a cerium containing nodularizing agent, from which concluded that the nodular graphite is nothing but a spherulite consisting of innumerable columnar crystals of graphite grown radially from a neucleus in the direction of the c axis. The occurrence, on the contrary, of the imperfection of spherulitic graphite or the various patterns of spherulitic graphite, consisting of a few columnar crystals, seems to be caused by the insufficient deoxidation and insufficient undercooling of the liquid of nodular iron.
Lately he found out another pattern of imperfect graphite spherulite, i.e. a dendritic form of graphite a which was observed in Ni-C melt by I. Minkoff and I. Einbinder, in conjunction with a perfect graphite spherulite.
From the electron-microscopic observation of this dendritic graphite it may be concluded that the dendrite is also an assembly of some columnar crystals of graphite grown from neuclei lying along the principal trunk of the dendrite, and the branches of the dendrite have no exact crystallographic interrelation with the principal axis of the dendrite. This is quite different from a normal dendrite consisting wholly of a single crystal. The fact also proves that there is no essential difference between the spherulititic growth and the dendritic growth of graphite. Both of them consist of columnar crystals of graphite, the former consisting of innumerable columnar crystals grown from a common neucleus and the latter of a small number of columnar crystals grown arbitrarily from neuclei which are scattered along the principal axis of the dendrite.