Mechanically activated synthesis studied by X-ray diffraction in the Fe-Al system

The nanocrystalline phase formation in the Fe-Al binary system induced by a new low temperature process, called mechanically activated self-propagating high-temperature synthesis (MASHS)', was investigated by X-ray diffraction (XRD) analysis. Some parameters of this alternative powder processing method which associates a short ball milling duration (leading to nanoscale 3-D polyinterfaces of the elemental components) and a self-propagating high-temperature synthesis (SHS) reaction, were studied. Their influence on the solid (liquid) state kinetic paths of phase formation was characterized. The XRD profile line analysis shows that it is possible to synthesize, for example, an FeAl intermetallic compound possessing a nanostructure (40 nm) using the MASHS process. Moreover, an infrared camera revealed that the mechanical activation step implemented before the SHS process decreases the ignition temperature of the exothermic reaction (100 K) between pure Fe and Al, whatever the composition. (C) 1999 Elsevier Science S.A. All rights reserved.