Effect of Oxides on Nucleation Behaviour in Supercooled Iron

Abstract

As a part of the study on the effect of oxides on heterogenuous nucleation during iron solidification, the effects of Al₂O₃, SiO₂, and rare earth oxides were examined, by measuring the critical supercooling of 300g electrolytic iron under special slag in a Tammann furnace. The following results have been obtained.
1) The critical supercooling for heterogenuous nucleation is remarkably lowered than that of homogenuous nucleation. This value is 3°C by the addition of R. E. M, and this is extremely small when compared with 14°C by Al₂O₃, 30°C by SiO₂, and 53°C by MnO.
2) The heterogenuous nucleating potency of oxide catalyzers is dependent upon the difference of interfacial energy between the oxide substrate and δ-Fe. This interfacial energy can be theoretically explained by the disregistry between both crystals.