Partially amorphous Fe57Co21Nb7B15 powder mixture was prepared by mechanical alloying in a high energy planetary ball-mill under argon atmosphere. Thermal stability, magnetic properties, structural and morphological changes during the milling process were followed by differential scanning calorimetry, vibrating sample magnetometry. X-ray diffraction and scanning electron microscopy. A duplex nanostructure of Fe(Co) and Fe-boride nanocrystals within an amorphous matrix is achieved on further milling time. Depending on the structural state of the milled powders, two or several overlapping exothermic peaks over the temperature range 100-700 degrees C were revealed in the DSC scans. The saturation magnetization and coercivity values are of about 111 emu g(-1) and 59 Oe, respectively, after 96 h of milling. (C) 2011 Elsevier B.V. All rights reserved.