Roberto Orrù, Roberta Licheri, Antonio Mario Locci, Giacomo Cao, Jimmy De Wilde, Fabienne Lemoisson, Ludo Froyen, Inigo A. Beloki, Alexander E. Sytschev, Alexander S. Rogachev, David J. Jarvis Self-propagating combustion synthesis of intermetallic matrix composites in the ISS 1. Introduction Self-propagating combustion synthesis reactions are character- ized by the fact that, once ignited by an external energy source, they are able to propagate in the form of a combustion wave through the reacting mixture without requiring additional ener- gy [1]. This type of reaction has been exploited to establish the technique referred to in the literature with the acronym of self- propagating high-temperature synthesis (SHS). The latter per- mits to obtain a variety of advanced materials, such as ceramics, intermetallics, composites, solid solutions, functionally graded materials, and so on [1]. The SHS method has received attention for its simplicity, short reaction time, easy-to-build equipment, low energy requirements, and possibility of obtaining complex or metastable phases. It is well known that several parameters affect combustion synthesis reactions. For instance, reaction stoichiometry, green density, reactants-particle size, heating and cooling rates, as well as the presence of a gravitational field, are © Z-Tec Publishing, Bremen Microgravity sci. technol. XIX-5/6 (2007) Roberto Orrù, Roberta Licheri et al: Self-propagating combustion synthesis of intermetallic matrix composites in the ISS 85 Combustion Synthesis experiments have been performed on the ISS (International Space Station) during the Belgian taxi-flight mission ODISSEA in November 2002, in the framework of the ESA-coordinated project COSMIC (Combustion Synthesis under Microgravity Conditions). The main objective of the experiments was to investigate the general physico-chemical mechanisms of combustion synthesis processes and the forma- tion of products microstructure. Within the combustion zone, a number of gravity-dependent phenomena occur, while other phenomena are masked by gravity. Under certain conditions, gravity-dependent secondary processes may also occur in the heat-affected zone after combustion. To study the influence of gravity, a specially dedicated reactor ensemble was designed and used in the Microgravity Science Glovebox (MSG) onboard the ISS. In this work, the experiment design is first discussed in terms of the experimental functionality and reactor ensemble integration in the MSG. To investigate microstructure forma- tion, a sample constituted by a cylindrical portion followed by a conical one, the latter being inserted inside a massive copper block, is used. The experiment focused on the synthesis of inter- metallic matrix composites (IMCs) based on the Al-Ti-B system. Depending on the composition, different intermetallic com- pounds (TiAl and TiAl 3 ) can be formed as matrix phase while TiB 2 represents the reinforcing particulate phase. During the ISS mission, six samples with a relatively high green density of 65%TD have successfully been processed. The influence of the composition on the combustion process will be examined. Authors Roberto Orrù, Roberta Licheri, Antonio Mario Locci, Giacomo Cao Dipartimento di Ingegneria Chimica e Materiali, Centro Studi sulle Reazioni Autopropaganti (CESRA), Unita` di Ricerca del Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM) Università degli Studi di Cagliari, Cagliari, Italy, Jimmy De Wilde, Fabienne Lemoisson, Ludo Froyen Dept. MTM, K.U. Leuven Kasteelpark Arenberg 44, B-3001 Heverlee, Belgium Inigo A. Beloki INASMET, Parque Tecnologico E-20009 Donostia - San Sebastian, Spain Alexander E. Sytschev, Alexander S. Rogachev Institute of Structural Macrokinetics and Materials Science Russian Academy of Sciences Chernogolovka, Moscow Region, 142432 Russia David J. Jarvis European Space Agency Keplerlaan 1 - P.O Box 299 - 2200 Ag Noordwijk Zh - The Netherlands Correspondence Giacomo Cao Dipartimento di Ingegneria Chimica e Materiali Università degli Studi di Cagliari, Cagliari, Italy cao@visnu.dicm.unica.it