The toughening of alumina with iron: Effects of iron distribution on fracture toughness

Two composites have been fabricated by hot pressing powder blends of alumina with 20 volume percent of ductile iron particles. The composites differ in the shape, size and distribution of the iron particles. The fracture toughness of each composite has been obtained in situ, by testing inside a scanning electron microscope, using a double cantilever beam technique modified specifically for small ceramic specimens. Observation of the crack-particle interactions has enabled information to be gained about the toughening mechanisms occurring and hence the parameters for microstructural tailoring of these materials have been deduced Results showed that the fracture toughness of the composites differed greatly due to the distribution of the iron throughout the microstructure, which in turn affected the type and degree of observed toughening mechanism. These material-specific toughening parameters were then used to fabricate a third alumina/iron composite with a more optimised fracture toughness. (C) 1997 Elsevier Science Limited. All rights reserved.