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

Abstract

Combustion syntheses involving intermetallic and thermitic reactions were conducted to fabricate FeAl–TiB2–Al2O3 composites. Two combustion systems consisting of Fe, Al, Ti, Fe2O3 and B2O3 were studied for formation of xFeAl–yTiB2–Al2O3 composites with x = 1.5–3.5 and y = 0.5–0.8. In the reaction series, thermitic reduction of Fe2O3 and B2O3 by Al thermally activated the reaction between Fe and Al. As a result, the combustion wave of the synthesis reaction was sufficiently exothermic to propagate in a self-sustaining manner. With an increase in TiB2 and FeAl of the composites, the decrease of reaction exothermicity resulted in a decline of the combustion wave velocity and reaction temperature. The activation energy Ea = 88.92 kJ/mol was deduced for the synergetic combustion reaction. Based on XRD analysis, a thorough phase conversion was achieved and composites composed of FeAl, TiB2, and Al2O3 with different contents were obtained. The SEM micrograph showed the FeAl-based composite with a dense and connecting morphology.

Combustion Synthesis of NbB2–Spinel MgAl2O4 Composites from MgO-Added Thermite-Based Reactants with Excess Boron

“…In Reaction (1), the aluminothermic reduction of Nb 2 O 5 (the reaction enthalpy, ∆H r = −536 kJ/mol of Al 2 O 3 and the adiabatic temperature, T ad = 2756 K) is more energetic than that of B 2 O 3 (∆H r = −403.8 kJ/mol of Al 2 O 3 and T ad = 2315 K) [27,28]. The intermetallic reaction of Nb + 2B to yield NbB 2 with formation enthalpy ∆H f = −175.3 kJ/mol and T ad = 2315 K is exothermically comparable to the B 2 O 3 + 2Al reaction [29].…”

Intermetallic/Ceramic Composites Synthesized from Al–Ni–Ti Combustion with B4C Addition

“…However, both poor ductility and low fracture toughness hinder the extensive industrial use of Niand Ti-aluminides [5][6][7]. An effective way to improve their mechanical properties is to fabricate intermetallic-based composites, where reinforcing ceramic phases such as carbide, boride, nitride, and oxide are added [8][9][10][11].…”

Formation of Mo5Si3/Mo3Si–MgAl2O4 Composites via Self-Propagating High-Temperature Synthesis

“…The SHS process has the merits of high energy effectiveness, short reaction time, simple operation, and good purification capability [15][16][17]. Aluminothermic reduction of metal oxides is thermally beneficial for combustion synthesis of materials with low formation enthalpies and provides in situ generation of Al 2 O 3 [18][19][20]. The SHS reaction combined with aluminothermic reduction was conducted with green compacts made up of MoO 3 , SiO 2 , Al, and MgO for the synthesis of MoSi 2 -and Mo 5 Si 3 -MgAl 2 O 4 composites [21].…”