Influence of milling conditions on the FeAl intermetallic formation by mechanical alloying

The formation of FeAl intermetallic compound by mechanical alloying has been investigated as a function of milling time. Mixtures of elemental powders of Fe and Al are progressively transformed into a disordered solid solution characterized by an average composition of Fe-35at.%Al. Changes in powder morphology, the degree of reaction advancement, as well as crystallite size and microstress evolution have been described. It has been found that the iron crystallite size tends to about 15 nm and that FeAl grains of the same size are formed. Mössbauer spectroscopy (MS) study has provided additional information about intermediate solid solutions, the final composition and the influence of the milling velocity on FeAl formation. No free iron has been detected in powders processed for 24 h at the highest rotation speed (400 rev min −1). MS appears to be a unique technique that can provide unequivocal information about the state of mixed powders, especially for long milling times.