Observations on the mechanical integrity of a thin film composite interface model

The mechanical integrity of a thin film model of an aluminum/graphite metal matrix composite interface and the effect of electrical state on the locus of failure was studied. The physical thin film interface model consisted of a substrate of highly oriented pyrolitic graphite, an interfacial layer of reactively evaporated aluminum, and an overlayer of aluminum. The reactive evaporation of aluminum occurred in atmospheres of varying oxygen and hydrogen content. The thickness of the interfacial layer was 50 nm and the aluminum overlayer was 150nm thick. A fracture mechanics model incorporating residual stresses was used to define the locus of failure in the physical model in terms of fracture toughness. Electrostatic stresses at the interface were proposed as a possible factor in modifying the locus of failure by electronic effects. Experimental systems were designed and constructed to study the locus of failure in and the electrical properties of the physical interface model. The chemistry and microstructure of the interfacial layer were found to vary the locus of failure in the vicinity of the graphite-reactive layer interface.