Fully self-consistent all-electron density functional calculations have been performed to obtain the full adhesion curves for the systems NiAl, Cr, and NiAl-Cr. We find that the work of adhesion for Cr is larger than that for NiAl and for the interface between these two materials the work of adhesion is intermediate. We find that NiAl at the NiAl-Cr interface is Ni-terminated. Electronic charge density distributions indicate that the bonding is largely metallic with a discernible covalent character. The interfacial bonding is due largely to the Ni and Cr d electrons while in NiAl the bonding results from sp-d hybridization. Estimates of segregation effects suggest a reduction of the work of adhesion for the interface by roughly 20%. Comparisons between our calculated ideal work of adhesion and fracture toughness measurements indicate that significant crack-tip plasticity is associated with the brittle fracture mechanism of NiAl. Our results are consistent with previous electronic structure calculations and measurements on NiAl and fracture mechanisms observed for NiAl-Cr composites. © 1996 The American Physical Society.

• Received 13 November 1995

DOI:https://doi.org/10.1103/PhysRevB.53.13883