Iron-alumina composites: From discrete iron particles to interconnected iron network. Powder synthesis, spark plasma sintering, microstructure and mechanical properties

The aim is to prepare Fe-Al2O3 ceramic-matrix composites with a high Fe content in order to benefit from a high degree of toughening. Fe-Al2O3 powders with different Fe contents (14.2-47.4 vol%) are prepared by selective reduction in H2 of the corresponding amorphous Al2-2xFe2xO3 oxides, themselves prepared by decomposition in air of the mixed oxalates. Dense samples are prepared by Spark Plasma Sintering. The samples are investigated by thermal analysis, scanning electron microscopy and X-ray diffraction. The microhardness, fracture strength and toughness are discussed with respect to the composition and the microstructure, i.e. a dispersion of discrete Fe particles or a continuous Fe network into the alumina matrix. The latter samples are significantly thougher than the former ones (about 14 and 8 MPa m1/2, respectively).