In Situ Formation of TiB2/Al2O3-Reinforced Fe3Al by Combustion Synthesis with Thermite Reduction

Fabrication of Fe3Al-TiB2-Al2O3 composites with a broad range of phase compositions was studied by combustion synthesis involving aluminothermic reduction of oxide precursors. Two reaction systems composed of elemental Fe, amorphous boron, and a thermite mixture of Fe2O3/TiO2/Al were conducted in the mode of self-propagating high-temperature synthesis (SHS). One was to produce the composites of 1.25Fe(3)Al + xTiB(2) + Al2O3 with x = 0.3-1.0. The other was to fabricate the products of yFe(3)Al + 0.6TiB(2) + Al2O3 with y = 1.0-1.6. Reduction of Fe2O3 by Al acted as an initiation step to activate the SHS process. Complete phase conversion from the reactants to Fe3Al-TiB2-Al2O3 composites was achieved. The variation of combustion front velocity with sample stoichiometry was consistent with that of the reaction exothermicity. Based on combustion wave kinetics, the activation energy of E-a = 86.8 kJ/mol was determined for formation of the Fe3Al-TiB2 -Al2O3 composite through the thermite-based SHS reaction. In addition, with an increase in TiB2 , the fracture toughness of the 1.25Fe(3)Al + xTiB(2) + Al2O3 composite was found to increase from 5.32 to 7.92 MPa.m(1/2).