THE TOUGHENING OF ALUMINA WITH IRON - EFFECTS OF IRON DISTRIBUTION ONFRACTURE-TOUGHNESS

Two composites have been fabricated by hot pressing powder blends of a lumina with 20 volume percent of ductile iron particles. The composite s differ in the shape, size and distribution of the iron particles. Th e fracture toughness of each composite has been obtained in situ, by t esting inside a scanning electron microscope, using a double cantileve r beam technique modified specifically for small ceramic specimens. Ob servation of the crack-particle interactions has enabled information t o be gained about the toughening mechanisms occurring and hence the pa rameters for microstructural tailoring of these materials have been de duced Results showed that the fracture toughness of the composites dif fered greatly due to the distribution of the iron throughout the micro structure, which in turn affected the type and degree of observed toug hening mechanism. These material-specific toughening parameters were t hen used to fabricate a third alumina/iron composite with a more optim ised fracture toughness. (C) 1997 Elsevier Science Limited. All rights reserved.