Rapid synthesis of Al2O3 reinforced Fe–Cr–Ni composites

Short distance infiltration (sdi) was used to fabricate metal matrix composites (MMC) with very fine ceramic reinforcements. This ‘sdi-MMC’ process was used to synthesize a dense composite comprised of Fe–Cr–Ni/Al2O3. Fe2O3/Fe/Ni/Cr/Al powder compacts were rapidly heated to 900 °C and held at this temperature and a pressure of 20 MPa in air for 5 min. This thermomechanical treatment triggered the highly-exothermic thermite reaction between starting powders that, in turn, resulted in rapid in-situ formation of a composite comprised predominantly of γ(fcc) Fe–Cr–Ni, along with smaller amounts of α(bcc) Cr–Fe–Ni and α-alumina. SEM and TEM analyses revealed a microstructure consisting of a uniformly dispersed network of very fine (a few hundred nanometers) Al2O3 grains in a matrix of a fine-grained (=5 microns) metallic alloy. The dense composites exhibit average bend strength and toughness values of 1100 MPa and 18 MPa (m)1/2, respectively.