Synthesis, microstructure and mechanical properties of (Mo,Ti)Si2/Al2O3 composites prepared by thermite-reaction-assisted combustion synthesis

(Mo0.95Ti0.05)Si-2/3.3mol%Al2O3 composites were synthesized by self-propagating high-temperature synthesis using Mo, Si, Al and TiO2 powders. The addition of alloying element Ti to MoSi2 and the synthesis of reinforcing particulate Al2O3 phase were achieved through the thermite reaction, Al + TiO2 -> Ti + Al2O3. The results showed that the combustion synthesis reaction mode in the Mo, Si, Al and TiO2 reaction mixture was spiral and self-propagating, and the reaction product was composed of MoSi2, (Mo,Ti)Si-2 and Al2O3. The combustion products were consolidated by vacuum hot-pressing at 1773 K and 27.5 MPa for 90 min to consolidate composites with relative densities above 95% of theoretical. The hot-pressed (Mo0.95Ti0.05)Si-2/3.3mol%Al2O3 composite with relative density of 97.5% exhibited finer microstructure and superior mechanical properties compared to MoSi2 monolithic material; Vicker's hardness of 12.9 GPa, bending strength of 320 MPa and fracture toughness of 3.37 MPa m(1/2). (C) 2016 Elsevier B.V. All rights reserved.