Effect of iron morphology and interfacial bonding on the toughening of Al2O3/Fe composites

Two morphologically different composites comprising an alumina matrix and 2 0 vol. pct Fe particles have been fabricated by hot pressing technique. Two kinds of microstructures, i.e. a dispersive distribution of Fe particles a nd a network distribution of Fe particles in alumina matrix, have been prod uced. Both composites are tougher than the virgin alumina matrix. The fract ure toughness of the composite with a network microstructure is much higher than the composite with a microstructure of dispersed particles. For the p articulate dispersion microstructure, the main limitation to the toughening is the lack of plastic deformation of the ductile Fe due to the pull out o f Fe particles, indicating weak bonding at the Al2O3/Fe interface. For the network microstructure composite, the gauge length of the ductile phase is much larger, allowing the ductile Fe to be stretched to failure between the crack faces. The weak bonding at Al2O3/Fe interface can promote partial de bonding and contribute further to toughening in the network microstructure composite.