INFLUENCE OF MILLING CONDITIONS ON THE FEAL INTERMETALLIC FORMATION BY MECHANICAL ALLOYING

The formation of FeAl intermetallic compound by mechanical alloying ha s been investigated as a function of milling rime. Mixtures of element al powders of Fe and Al are progressively transformed into a disordere d solid solution characterized by an average composition of Fe-35 at.% Al. Changes in powder morphology, the degree of reaction advancement, as well as crystallite size and microstress evolution have been descri bed. It has been found that the iron crystallite size tends to about 1 5 nm and that FeAl grains of the same size are formed. Mossbauer spect roscopy (MS) study has provided additional information about intermedi ate solid solutions, the final composition and the influence of the mi lling velocity on FeAl formation. No free iron has been detected in po wders processed for 24 h at the highest rotation speed (400 rev min(-1 )). MS appears to be a unique technique that can provide unequivocal i nformation about the state of mixed powders. especially for long milli ng times.