Amorphous Fe-Al alloys obtained by mechanical alloying

The amorphization processes by mechanical alloying in the Fe-Al system have been studied for several compositions, including the ones corresponding to equilibrium FeAl2, Fe2Al5 and FeAl3 intermetallic compounds. Mixtures of pure crystalline metal powders containing from 60 to 85 at.% Al and low energy ball milling have been applied for alloys synthesis. X-ray diffraction, differential scanning calorimetry and transmission electron microscopy were utilized to monitor the structural and phase transformations through different stages of milling. For all alloys studied mechanical alloying resulted in an amorphous structure formation. In equilibrium conditions the stable intermetallic compounds exist in this composition range, however, their formation by solid state reaction has been kinetically suppressed and an amorphous phase appeared. Heating the samples in the DSC resulted in the crystallization of the synthesised amorphous alloys and equilibrium intermetallic compounds appeared. However, for Fe-60 and 75 at.% Al alloys, the phases corresponding to a lower Al content were only detected, i.e. FeAl and Fe2Al5, respectively. The formation of metastable FeAl6 compound at the first stage of the crystallization process of Fe-85 at.% Al alloy has been observed.