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

Abstract

Fabrication of Fe 3 Al-TiB 2-Al 2 O 3 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 Fe 2 O 3 /TiO 2 /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 + Al 2 O 3 with x = 0.3-1.0. The other was to fabricate the products of yFe 3 Al + 0.6TiB 2 + Al 2 O 3 with y = 1.0-1.6. Reduction of Fe 2 O 3 by Al acted as an initiation step to activate the SHS process. Complete phase conversion from the reactants to Fe 3 Al-TiB 2-Al 2 O 3 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 Fe 3 Al-TiB 2-Al 2 O 3 composite through the thermite-based SHS reaction. In addition, with an increase in TiB 2 , the fracture toughness of the 1.25Fe 3 Al + xTiB 2 + Al 2 O 3 composite was found to increase from 5.32 to 7.92 MPa•m 1/2 .

Combustion Synthesis of FeAl-based Composites from Thermitic and Intermetallic Reactions

“…A number of manufacturing methods have been applied to produce ceramics-iron aluminide composites, including mechanochemical synthesis [14], spark plasma sintering [15], hot pressing [16], liquid-phase sintering [17], thermal explosion [18] and self-propagating high-temperature synthesis (SHS) [19,20]. Combustion synthesis in the SHS sense is recognized by its high energy effectiveness, rapid reaction process, easy operation, diversity of products, and in situ formation of composite components [21][22][23].…”