Phase equilibria in ternary nickel-carbide alloys

Using analysis and generalization of 11 experimentally constructed phase diagrams of the ternary Ni-Me′C-Me″C systems, where Me stands for the heat-resistant group IV and V metals, it was established that these phase diagrams can be divided into two categories: diagrams with a monovariant eutectic, and diagrams with a ternary eutectic whose formation is related to the binodal decomposition of carbide solid solutions. The type-I diagrams form when the carbide crystalline lattice parameter ratio α1/α2 &le 1.051, while the type-II diagrams form when α1/α2 ≥ 1.056. Depending on the dimensional factor in the cast rapidly cooled eutectic alloys, four categories of nonequilibrium state can be observed.