Calculation of the interfacial energy of B1-type carbides and nitrides with austenite

The interfacial energy of NaCl (B1)-type carbides and nitrides that have a cube-on-cube orientation relationship with austenite was calculated using a discrete lattice-plane (DLP), nearest-neighbor broken-bond (NNBB) method. The required bond energies were evaluated from Miedema's semiempirical model for alloys and available thermodynamic data. For Ti, V, Zr, and Nb carbides and nitrides, a significant chemical interfacial energy arises from the large difference in the concentration of nonmetallic atoms between austenite and the compound phase. In contrast to binary fcc/fcc cases, where (111)-type interfaces have the smallest interfacial energy, (100)- and (111)-type interfaces have been found to have the smallest and the largest energy, respectively, of all orientations. The structural component of the interfacial energy arising out of lattice misfit is likely to be larger than the chemical component for these compounds. The orientation dependence of the total interfacial energy and the associated Wulff construction indicate that, due to the retention of the strong anisotropy of the chemical interfacial energy, the equilibrium shape of these B1 compounds is a cube, possibly with facets at corners and edges over a wide temperature range.