First principles study of effect of lattice misfit on the bonding strength of Ni/Ni3Al interface

By using a discrete variational X-alpha (DV-X-alpha) method, the electronic structures and bonding strengths of Ni/Ni3Al (or gamma/gamma') interface with different lattice misfits (delta) were calculated in the framework of the nonrelativistic first-principles theory. In order to describe the effect of d on the interfacial binding strength and the structural stability of coherent gamma/gamma' interface, we calculated the interfacial binding covalent bond density (CBD) and the local environmental total bond overlap population (LTBOP). Very obvious effects of lattice misfits on the electronic structures of coherent gamma/gamma' interface were found. On one hand, less than -0.6% negative lattice misfit can increase the binding strength of the gamma/gamma' interface. On the other hand, the local environmental total bonding strength of the gamma/gamma' interface decreases with increasing magnitude of delta. Therefore, the magnitude and sign of lattice misfit must be carefully controlled to balance the high-temperature creep strength of Ni-base single crystal superalloy and the structural stability of the gamma/gamma' interface when one designs new alloys. (C) 2004 Kluwer Academic Publishers.