Presentation on theme: "Dragica M. Minić a Ljiljana Mihajlović a A.Leksandra Gavrilović b Lidija Rafailović b Dušan M. Minić c Corresponding author: Tel +381-11-3336-689; E-mail."— Presentation transcript:
Dragica M. Minić a Ljiljana Mihajlović a A.Leksandra Gavrilović b Lidija Rafailović b Dušan M. Minić c Corresponding author: Tel ; address: a Faculty of Physical Chemistry, University of Belgrade, Belgrade, Serbia b ECHEM Kompetenzzentrum für Angewandte Elektrochemie GmbH, Wiener Neustadt, Austria c Military Technical Institute, Belgrade, Serbia References 1. T. Kulik, Journal of Non-Crystalline Solids. 2001, 287, A.A. Soliman, S. Al-Heniti, A. Al-Hajry, M. Al-Assiri, G. Al-Barakati, Thermochim. Acta 2004, 413, D. M. Minić, A. Gavrilović, P. Angerer, D.G. Minić, A. Maričić, Journal of Alloys and Compounds 2009, 476, P. Budrugeac and E. Segal, Rev. Roum. Chim., 2004, 49, L.A. Perez-Maqueda, J.M. Criado, f. J. Gotor and J. Malék, J. Phy.Chem., 2002, 106, Acknowledgements The investigation was partially supported by the Ministry of Science and Environmental Protection of Serbia, Project Kinetics of structural transformations of Fe 75 Ni 2 Si 8 B 13 C 2 amorphous alloy induced by thermal treatment Introduction 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 Fe 75 Ni 2 Si 8 B 13 C 2 amorphous alloy in temperature range K by resolution multi-step process to single steps. Experimental procedures The ribbon-shaped samples of Fe 75 Ni 2 Si 8 B 13 C 2 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 Fe 75 Ni 2 Si 8 B 13 C 2 amorphous alloy is stable up to 723K when the multi-step of crystallization began giving the overlapping crystallization peaks in the temperature range of K . Fig.1 DSC curves at two heating rates: a) as-recorded; b) resolved curves. 5 K min K min -1 S Fig. 2. X-ray diffraction patterns the as-prepared alloy and after thermal treatment at given temperatures. Fe 3 SiFe 2 BFe 15 Si 3 B 2 Annealing Temperature [K] Crystallite size [nm] Weight fraction [wt. %] Crystallite size [nm] Weight fraction [wt. %] Crystallite size [nm] Weight fraction [wt. %] ± 1 27 ± ± ± ± ± ± 1 10 ± 1 7 ± 2 36 ± 6 52 ± ± ± ± 1 13 ± Overall values Peak 1Peak 2Peak 3 KissingerOzawaKissingerOzawa Kissinge r Ozawa E a [kJ mol -1 ] ln A 375.1± ± ± ± ± ± ± ± ±8 47± ±8 41±12 ff Fig.3 The application of Perez-Maqueda criterion on the set Avrami-Erofeev equations for all four heating rates. 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 E a = 323 ± 9 kJ mol –1, ln A = 47 ± 1.3 min –1, for first step; E a = 304 ± 13 kJ mol –1, ln A = 43.1 ± 1.8 min –1, for the second step and E a = 276 ± 20 kJ mol –1, ln A = 38.4 ± 5.0 min –1, for the third step of crystallization.