Crystallization Kinetics of the Fe68Nb6B23Mo3 Glassy Ribbons Studied by Differential Scanning Calorimetry

Abstract

Fe-based metallic glass has wide industrial application due to its unique mechanical behavior and magnetic properties. In the present work, the non-isothermal crystallization kinetics in Fe68Nb6B23Mo3 glassy alloys were investigated by differential scanning calorimeter (DSC). The results indicate that both the glass transformation and crystallization process display an obvious kinetic effect. The activation energy is calculated using Kissinger’s method and Ozawar’s method. The activation energy for Tg (glass transition temperatures), Tx (crystallization initiation temperatures) and Tp (crystallization peak temperatures) calculated from Kissinger equation, is 308 ± 4, 342 ± 5 and 310 ± 7 kJ mol−1, respectively. The activation energy for Tg, Tx and Tp calculated from Ozawa equation is 322 ± 3, 356 ± 5 and 325 ± 7 kJ mol−1, respectively. With the increase of the crystallization volume fraction x, the Avrami exponent n(x) first decreases and then increases. At the preliminary step, 0 < x < 0.25, 2.5 < n(x) < 4.0 stands for the growth from a small size with an increasing nucleation rate. When 0.25 < x < 0.71, n(x) decreases from 2.5 to 1.5, indicating that this stage is controlled by the growth of small particles with a decreasing nucleation rate.

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“…Likewise, there are other linear methods (normally based on the determination of the peak temperature). However, the activation energy was similar to those calculated by Kissinger, and the differences are based more on the linear relationships established between This work's values are in the same relatively wide range [28][29][30][31][32][33][34]. The shift in the activation energies can be related to different composition and microstructure (including crystallographic defects).…”

“…Likewise, there are other linear methods (normally based on the determination of the peak temperature). However, the activation energy was similar to those calculated by Kissinger, and the differences are based more on the linear relationships established between the parameters than on real differences in the crystallisation process [29]. For example, representing ln (β/T p 2 ) is not the same as representing ln (β/T p ) (in both cases as a function of the inverse of the peak temperature).…”

“…Thus, the activation energy corresponds to the crystal growth mechanism. In nanocrystalline alloys with similar composition, the same phenomenon was detected [25][26][27][28][29][30][31][32][33][34]. At high transformed fractions, the degree of transformation slows down and the local activation energy decreases [44], probably due to the higher influence of the diffusion as main mechanism.…”

“…The calculated energies of this work are compared with some of those found in the scientific literature (applying Kissinger method) in Table 1. This work's values are in the same relatively wide range [28][29][30][31][32][33][34]. The shift in the activation energies can be related to different composition and microstructure (including crystallographic defects).…”