Preparation and characterization of alumina-iron cermets by hot-pressing of nanocomposite powders

Alumina composites with 0-36 vol% iron metal dispersed inclusions have been prepared by a new processing route. Nanostructured powders were synthesized by a high energy dry ball-milling process and then consolidated by sintering at 1700 K under a pressure of 30 MPa. The materials consist of micrometre-size Al2O3 with metallic Fe in isolated regions from 10 mu m down to nanometre size. From low to high metallic contents, the same type of interwoven microstructure is observed. Hardness, elastic and shear moduli, fracture toughness and the size of the inclusions vary regularly with the metal content. Addition of metal increased the fracture toughness from 3.0 to 8 MPa m(1/2).