The Fe80-xNi20Six (x = 0, 5, and 10) nanocrystalline soft magnetic powders were successfully prepared via mechanical alloying (MA) route in a planetary ball mill at different milling times. The evolution of the microstructure, phase analysis, and magnetic properties during the milling process was studied using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and a vibrating sample magnetometer (VSM). SEM observations indicated that different morphologies were obtained during the MA stages. XRD results showed that an alpha-(Fe (Ni-Si)) solid solution was formed after 10 h of MA and an estimated crystallite size for the Fe80Ni20 alloy after 36 h of MA was about 14 nm, which this size was reduced to about 6 nm after the addition of 10 at.% Si. An increase in lattice strain was observed by increasing the milling time and Si concentration. The VSM analysis indicated that a higher amount of Si would lead to lower values of saturation magnetization. In addition, coercivity increased during MA, reaching a maximum at 10 h of MA, and finally decreased with further MA times. This latter effect could be attributed to the effect of very fine crystallite size, obtained after prolonged milling. (C) 2013 Elsevier B.V. All rights reserved.