Fe40Ni40B6P14 and Fe40Ni40Si6P14 alloys, in both a nanostructural and a disordered amorphous-like state, were produced from different precursors using the ball milling technique. The development of such metastable phases was investigated by X-ray diffraction, differential scanning calorimetry and scanning electron microscopy. After the first 20 h, the diffraction peaks of the precursors disappeared, and the deformation during milling reduced the crystallite size of the alloys to 3-6 nm. The final crystallite size of the powders depended on the composition of the material as well as on the precursors utilized. The differential scanning calorimetry results revealed several exothermic peaks, indicating the crystallization of the amorphous-like state. The crystallization enthalpy was evaluated and the values obtained presented a maximum after 35 h of milling. The results were compared with data for rapidly quenched materials. The effect of the milling conditions on phase formation was analyzed. © 1994.