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, abnormally 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 discussed, in terms of a coarsening mechanism, depending on the atomic structure of the interface. For faceted grains with an atomically smooth interface structure, the coarsening was suggested to occur via two‐dimensional nucleation and a lateral‐growth mechanism. For spherical grains with an atomically rough interfacial structure, diffusion was suggested to control the coarsening process.