EFFECT OF THE ELECTRONIC STATE, STOICHIOMETRY AND ORDERING ENERGY ON THE DUCTILITY OF TRANSITION METAL-BASED INTERMETALLICS

The planar defects associated with deformation in ordered intermetallic compounds namely, the antiphase boundary, superlattice intrinsic stacking fault, and complex stacking fault are non-equilibrium structures corresponding to a state of disorder within the ordered structure of the lattice and therefore affect both the electronic energy states and the Brillouin zone structure. It is possible that a relationship exists between the antiphase boundary energy, gamma(APB), and the sum of the number of unfilled outermost d-state electrons in the transition metals on which this class of intermetallics is based. If this hypothesis is taken in conjunction with a set of rules for improving ductility in intermetallics proposed previously, a coherent explanation of recently observed ductilities in transition metal-based intermetallics would seem to be feasible.