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 i nvolves mainly the combination of two steps; the first step, a mechanical a ctivation, where pure elemental (Fe + Al) powders were co-milled inside a p lanetary mill, for a short time at given frequency and energy shacks and, t he second step, a self-propagating high-temperature synthesis (SHS) reactio n, 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 forma tion 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 thro ugh the sample, the time-resolved X-ray diffraction experiment (TRXRD) usin g synchrotron radiation coupled with an infrared thermography allows the il l situ study of the phase formation and the temperature evolution during th e MASHS process. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Scie nce Ltd. All rights reserved.