Shape dependence of the coarsening behavior of niobium carbide grains dispersed in a liquid iron matrix

In niobium carbide-iron (NbC-Fe) specimens where the grains,were faceted, a bnormally large grains appeared during coarsening, Normal and uniform grain growth occurred when the grain shape was changed to a spherical morphology by the addition of a small amount of boron. The results have been discusse d, in terms of a coarsening mechanism, depending on the atomic structure of the interface. For faceted grains with an atomically smooth interface stru cture, the coarsening was suggested to occur via two-dimensional nucleation and a lateral-growth mechanism. For spherical grains with an atomically ro ugh interfacial structure, diffusion was suggested to control the coarsenin g process.