Interfaces in continuous filament-reinforced Al{sub 2}O{sub 3}/NiAl composites

Interfacial structures in a continuous AlO{sub 3} filament-reinforced NiAl composite were investigated by transmission electron microscopy (TEM). A graphite phase, which is an artifact of the composite fabrication procedure, decorates the interfacial region of the composite. The presence of the graphite is believed to play a role in both the low interfacial bond strength in the as-fabricated composite and the further reduction in bond strength after 10 thermal cycles in the temperature range of 373 to 1,373 K. In regions where the graphite phase was not present, there appeared to be an intimate bond between the NiAl matrix and the Al{sub 2}O{sub 3} filaments. Simulation of TEM diffraction contrast images based upon a three-dimensional (3D) finite element analysis was employed to investigate the nature of the residual strains in regions along the interface. The simulations suggested that radial residual strains within the Al{sub 2}O{sub 3} filaments were randomly distributed along the interface. These strains are believed to be related to dislocation nucleation in the NiAl, which results from the relaxation of the thermally generated residual stresses.