f. f. Kinetics of structural transformations of Fe 75 Ni 2 Si 8 B 13 C 2 amorphous alloy induced by thermal treatment. S. Introduction
Kinetics of structural transformations of Fe75Ni2Si8B13C2 amorphous alloy induced by thermal treatment
Metallic glasses are kinetically metastable and thermodynamically unstable materials and undergo transformation to more stable crystal forms at higher temperatures . The change of structure can lead to change in their technologically important properties, such as the heat capacity, electrical resistivity, volume and magnetic properties . This imposes the importance of studying thermal properties and kinetics of phase transformations induced by thermal treatment of amorphous alloys.
The present paper is concerned with the non-isothermal kinetics of multi-step process of structural transformations of Fe75Ni2Si8B13C2 amorphous alloy in temperature range 293-1273 K by resolution multi-step process to single steps.
Dragica M. Minića
Dušan M. Minićc
E-mail address: [email protected]
aFaculty of Physical Chemistry, University of Belgrade, Belgrade, Serbia
bECHEM Kompetenzzentrum für Angewandte Elektrochemie GmbH, Wiener Neustadt, Austria
cMilitary Technical Institute, Belgrade, Serbia
The ribbon-shaped samples of Fe75Ni2Si8B13C2 amorphous alloy were obtained by standard procedure of rapid quenching of the melt on a rotating disc.
The thermal stability of alloy and the structural transformations has been investigated by the differential scanning calorimetry (DSC) in a nitrogen atmosphere.
Results and discussion
The Fe75Ni2Si8B13C2 amorphous alloy is stable up to 723K when the multi-step of crystallization began giving the overlapping crystallization peaks in the temperature range of 790-860 K .
5 K min-1
20 K min-1
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The investigation was partially supported by the Ministry of Science and Environmental Protection of Serbia, Project 142025.
Fig. 2. X-ray diffraction patterns the as-prepared alloy and after thermal treatment at given temperatures.
Fig.1 DSC curves at two heating rates: a) as-recorded;
b) resolved curves.
The detail inspection of our results it was shown the best linearity (R > 0.995) for the set of conversion functions denoted as “An” based on the Avrami-Erofeev equation in general form where n=3/2, 2, 3, 4, concerning the process involving the nucleation and nuclei growth. To confirm the obtained kinetic model IKP method was associated with the Perez-Maqueda criterion [4-5].
The kinetic triplets for every step were established involving the conversion function f(α)=3(1-α)[-ln(1-α)]2/3 for all steps and invariant kinetic parameters Ea = 323 ± 9 kJ mol–1, ln A = 47 ± 1.3 min–1, for first step; Ea= 304 ± 13 kJ mol–1, ln A = 43.1 ± 1.8 min–1, for the second step and Ea= 276 ± 20 kJ mol–1, ln A= 38.4 ± 5.0 min–1, for the third step of crystallization.
Fig.3 The application of Perez-Maqueda criterion on the set Avrami-Erofeev equations for all four heating rates.