Heena Dhurandhar, 1 Ashmi T. Patel, 2 T. Lilly Shanker Rao, 3 Kirit N. Lad, 2 and Arun Pratap 4 Kinetics of Crystallization of Co-Based Multi-Component Amorphous Alloy ABSTRACT: Crystallization is a thermally activated process in non-crystalline and amorphous solids. The kinetics of the solid state phase transformations can be studied using thermal analysis techniques such as differential scanning calorimetry DSC. For the kinetic analysis of the crystallization process under non- isothermal conditions, the choice of a reliable method is very important. The methods for the analysis of non-isothermal data are, in general, derived by extending the formalism developed for isothermal condi- tions. Most methods for the kinetic analysis of crystallization processes rely on the isokinetic hypothesis to separate the kinetics of the transformation from its dependence on temperature. It is assumed that the transformation rate can be described by a differential equation separable in  transformed fraction and T temperature, i.e., for continuous heating regime, d/dT=1/kTf, where  is the heating rate, kT is the rate constant, and f is the kinetic function reaction model. The crystallization kinetics of glassy Co 66 Si 16 B 12 Fe 4 Mo 2 have been studied with DSC and analyzed using non-isothermal theoretical expres- sions. The Avrami exponent, n, frequency factor, A, and activation energy, E, of crystallization are evaluated using Matusita and Sakka MS and modified Kissinger equations. Besides, isoconversional kinetic analysis has been applied to DSC data for the determination of these different kinetic parameters. The isoconversional methods calculate E  values at progressive degrees of conversion, , without mod- elistic assumptions, and hence, this approach takes care of the variation of kinetic parameters with the fraction crystallized. The activation energy has been determined using both linear integral and differential isoconversional methods and also by the non-linear isoconversional method suggested by Vyazovkin and Wight. These methods are found to give consistent results for E. Furthermore, a comparison has been made among various kinetic parameters obtained using different approaches to investigate the relative applicability and usefulness of the proposed methods. KEYWORDS: crystallization, isoconversional, kinetic parameters, IKP method Introduction Magnetic amorphous alloys have excellent soft magnetic properties such as low coercivity, low hysteresis loss, high permeability, and high saturation magnetization. Hence, they are widely used in antitheft secu- rity systems, magnetic recording heads, magnetic sensors, large transformers, and electronic devices 1–4. It is generally believed that the good soft magnetic properties of melt-spun amorphous alloys are lost by annealing-induced crystallization 4. However, in the last decade, an improvement in soft magnetic properties has been reported in a number of multi-phase nanocrystalline Fe-based amorphous alloys 5–10. This clearly indicates that the study of the kinetics of crystallization of an amorphous system is a key subject of investigation providing new opportunities of designing and processing innovative alloys. While a substantial amount of work exists on the crystallization kinetics of Fe-based amorphous alloys 11–14, the same study on Co-based amorphous alloys is scarce 3,4,15–17. Furthermore, most of the investigations on these magnetic amorphous alloys are devoted to studying the effect of crystallization on magnetic properties 18 and have also used Mössbauer spectroscopy 4,19, while others have simply used the peak-shift method of Kissinger 16,19 to obtain the activation energy of the crystallization Manuscript received May 28, 2009; accepted for publication September 9, 2010; published online October 2010. 1 Condensed Matter Physics Laboratory, Applied Physics Dept., Faculty of Technology and Engineering, The Maharaja Sayajirao Univ. of Baroda, Vadodara 390 001, India, e-mail: heena0609@yahoo.co.in; Present address: Dept. of Electronics, Mukesh Patel School of Technology Management and Engineering, SVKM’s NMIMS deemed University, Vile Parle West, Mumbai—400 056 2 Condensed Matter Physics Laboratory, Applied Physics Dept., Faculty of Technology and Engineering, The Maharaja Sayajirao Univ. of Baroda, Vadodara 390 001, India. 3 Electronics Dept., Narmada College of Science and Commerce, Bharuch 392 011, India. 4 Condensed Matter Physics Laboratory, Applied Physics Dept., Faculty of Technology and Engineering, The Maharaja Sayajirao Univ. of Baroda, Vadodara 390 001, India, e-mail: apratapmsu@yahoo.com Journal of ASTM International, Vol. 7, No. 10 Paper ID JAI102577 Available online at www.astm.org Copyright © 2010 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.