Structural evolution of mechanically alloyed nanocrystalline Fe-28Al powders

Mechanical alloying (MA) has been utilized to synthesize many equilibrium and/or nonequilibrium phases. The structural evolution of iron aluminides mechanically alloyed from a powder mixture of iron and aluminum has been studied using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). It is found that, during mechanical milling under argon atmosphere, aluminum dissolves gradually into the bcc lattice of α-Fe, resulting in the formation of bcc-Fe3Al solid solutions, locally with B2-ordered structure in some region. TEM investigation indicates that NNAPBs are formed during MA. Nanocrystalline microstructure is achieved in powders after 25-h milling, with the grain size about 78 nm.