Interfacial Structure, Growth Kinetics and Mechanisms of the Proeutectoid Ferrite Reaction in Fe-C and Fe-C-X Alloys.

摘要

One major program was an experimental study of the interfacial structure of the broad faces of ferrite plates in an Fe-C-Si alloy. The second major investigation comprised an experimental study of the growth kinetics of grain boundary ferrite allotriomorphs as a function of reaction temperature and carbon content in high-purity Fe-C alloys. A supporting theoretical study of the stereology of grain boundary allotriomorphs was simultaneously conducted. The experimental study showed that at small undercoolings the measure parabolic rate constants for the thickening and lengthening of the allotriomorphs are as much as an order of magnitude less than those calculated assuming carbon diffusion-control; with increased undercooling, the measured growth rates approached more closely, but did not quite reach those calculated. This discrepancy was ascribed to the presence of a proportion of partially coherent facets at the boundaries of the allotriomorphs. It was concluded that the experimental method used during this investigation is the most satisfactory one for determining the true growth kinetics of grain boundary allotriomorphs presently available.