Discrete lattice plane analysis of Baker–Nutting related B1 compound/ferrite interfacial energy

The interfacial energy of B1 (NaCl)-type carbides and nitrides (designated ξ) having Baker–Nutting orientation relationship with ferrite (α), i.e. (001)α//(001)ξ and [110]α//[100]ξ, was studied by discrete lattice plane, nearest neighbor broken bond method. The carbide (or nitride) lattice was contracted along the [001] direction so as to make the two lattices isomorphous and coherent at all interface orientations. The chemical interfacial energy of this hypothetical compound is highly anisotropic due to the difference in the M (metal atom)–I (non-metallic atom) coordination number between, for example, (001)- and (100)-type interfaces that would be equivalent in a cubic lattice. As a result, the equilibrium shape is a square plate with (001) broad faces. The anisotropy of the strain energy arising out of a large misfit along the [001] direction may override the anisotropy of chemical energy and dictate the observed square plate morphology of carbides and nitrides in ferrite.