In this study, we have investigated the effect of substituting Mn for Fe on the crystallization kinetics of amorphous Fe73.5-xMnxCu1Nb3Si13.5B9 (x = 1, 3, 5, 7) alloys. The samples were annealed at 550 degrees C and 600 degrees C for 1 h under an argon atmosphere. The X-ray diffraction analyses showed only a crystalline peak belonging to the alpha-Fe(Si) phase, with the grain size ranging from 12.2 nm for x = 0 to 16.7 nm for x = 7. The activation energies of the alloys were calculated using Kissinger, Ozawa and Augis-Bennett models based on differential thermal analysis data. The Avrami exponent n was calculated from the Johnson-Mehl-Avrami equation. The activation energy increased up to x = 3. then decreased with increasing Mn content. The values of the Avrami exponent showed that the crystallization is typical diffusion-controlled three-dimensional growth at a constant nucleation rate. (C) 2008 Elsevier B.V. All rights reserved.