Characterization of iron aluminides formed in situ in an aluminium matrix composite

The application of quantitative metallography to the description of in situ formation of reinforcement in composites is presented. The dispersion of iron aluminides, formed from iron powder in an aluminium matrix during hot pressing in vacuum, was analyzed on images from a scanning electron microscope. It was found that the dispersion of a new phase formed at a temperature of 630 °C depended on the initial composition mixture of metal powders and time of pressing. Iron aluminides were formed by two mechanisms: by a regular diffusional growth and by self-propagating high-temperature synthesis (SHS). In the case of the formation of particles by the SHS mechanism, two types of very fine iron aluminides were noticed. They differed in size and shape.