Pressure-assisted SHS synthesis of MgAl2O4-TiAl in situ composites with interpenetrating networks

Self-propagating high-temperature synthesis (SHS) of compacted 2TiO(2)-Mg-4Al powder blends was used to fabricate in situ magnesium aluminate spinel-TiAl/Ti3Al interpenetrating phase composites, The combustion wave propagation and thermal explosion modes of SHS, as well as thermal explosion under uniaxial pressure (reactive forging) were investigated, with the samples' temperature closely monitored in the course of processing. SHS in 2TiO(2)-Mg-4Al blend was found to proceed in two stages. the leading reaction being the reaction between Mg and TiO2 with the formation of MgTiO3. Wave-like propagation of both leading and lagging reactions was observed during thermal explosion. The application of a moderate 60-80 MPa pressure during reactive forging at 800-900 degreesC yielded near fully dense (up to 98% of the theoretical density) MgAl2O4 spinel-TiAL/Ti3Al micrometer/submicrometer scale interpenetrating ceramic and intermetallic networks. The aluminide component had a very fine gamma + alpha(2) lamellar structure that should beneficially affect the toughness of the material synthesized. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.