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 alpha-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. (C) 2004 Elsevier B.V. All rights reserved.