Failure of metal–ceramic composites with spherical inclusions Original Research Article

In this work the development of cavities in spherical metal inclusions within a metal–ceramic composite and the subsequent influence upon the strength of the composite is investigated. A model experiment is undertaken whereby 100 μm diameter spherical aluminium inclusions are placed within an Al2O3–Al interpenetrating network composite. The samples are then fractured at temperatures ranging from room temperature to just below the melting temperature of aluminium. It is found that fracture originates from the aluminium inclusions and that there is clear evidence of cavitation in the ductile inclusions which also shows that these cavities formed as a result of high triaxial stress during cooling as a part of the fabrication process. This observation is supported by a numerical model of the stress formation and cavity growth process within an inclusion during cooling. The model also provides information on the effect of initial cavity size and location. Comparisons of experimental fracture strength and toughness data indicate that the observed high strength of these composites is explained by crack growth resistance due to ductile ligament bridging.