In situ time-resolved diffraction coupled with a thermal IR camera to study mechanically activated SHS reaction:: Case of Fe-Al binary system

Mechanically activated self-propagating high-temperature synthesis (MASHS) provides an attractive practical alternative to the conventional methods of producing intermetallic compounds, such as iron aluminides. This process involves mainly the combination of two steps; the first step, a mechanical activation, where pure elemental (Fe + Al) powders were co-milled inside a planetary mill, for a short time at given frequency and energy shacks and, the second step, a self-propagating high-temperature synthesis (SHS) reaction, which uses the exothermicity of the Fe + Al reaction. Once ignited with an external source, these reactions become self-sustained and propagate to completion within seconds. The combustion front directly leads to the formation of a nanometric Fe-Al intermetallic with a relative density of 70-80%. To understand this self-sustained reaction, an in situ study in real time was investigated on samples which differ by the shock power during milling and the compaction pressure (porosity). When the combustion front goes through the sample, the time-resolved X-ray diffraction experiment (TRXRD) using synchrotron radiation coupled with an infrared thermography allows the ill situ study of the phase formation and the temperature evolution during the MASHS process. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.