Comparative Study of VC, NbC, and TiC Interphase Precipitation in Microalloyed Low-carbon Steels

Interphase precipitation behavior of VC, NbC, and TiC during isothermal ferrite transformation in a series of microalloyed low-carbon steels with various amounts of carbide-forming alloying elements was comparatively investigated. Through the quantification by three-dimensional atom probe, the dispersion of alloy carbides formed by interphase precipitation was found to be higher in number density and smaller in size with more addition of carbide-forming elements or at lower transformation temperature. Moreover, although the dispersion of NbC and TiC was relatively finer than that of VC with the same amount of alloy addition, larger driving force for precipitation was necessary to obtain the same number density of NbC and TiC as that of VC. This deviation can be explained by the difference in amount of bulk alloy addition as well as interfacial energy between ferrite and alloy carbide, the latter of which was confirmed through the analysis based on Gibbs–Thomson effect.