Formation mechanism of Fe3Al and FeAl intermetallic compounds during mechanical alloying

Fe and Al elemental powder mixtures with composition Fe75Al25 and Fe50Al50 were mechanically alloyed in a planetary ball mill under different conditions. The structural changes of powder particles were studied by x-ray diffractometery and scanning electron microscopy. Mechanical alloying of Fe75Al25 and Fe50Al50 first produced a fine Fe/Al layered microstructure which transformed directly to the corresponding intermetallic compounds, Fe3Al and FeAl, with nanocrystalline structure at longer milling time. No intermediate phase, i.e. solid solution, was formed during mechanical alloying as a precursor to the intermetallic phase. The rate of mechanical alloying process was found to be dependent on milling variables such as rotation speed of mill, ball-to-powder weight ratio and number of milling balls.