1. Phase Transformation of Co 70 Fe 5 Si 10 B 15 Amorphous Alloy Induced by Heating D.M. Minić 1, A.M. Maričić 2, R.Z. Dimitrijević 3, 1Faculty of Physic al Chemistry, University of Belgrade 2 Technical Faculty Čačak, University of Kragujevac 3 Faculty of Mining and Geology, Department of Crystallography, University of Belgrade According to DSC measurements, the alloy crystallizes step by step with two well formed exothermal maxima at temperatures at about T1=460 C and T2=540 C, respectively. According to DSC measurements, the alloy crystallizes step by step with two well formed exothermal maxima at temperatures at about T1=460 C and T2=540 C, respectively. DSC curve of initial amorphous Co70Fe5Si10B15 alloy; heating rate10 C/min. DSC curve of initial amorphous Co70Fe5Si10B15 alloy; heating rate10 C/min. The thermal and kinetic values of the crystallization process were determined by analyzing the shifts of exothermal maxima in DSC thermograms depending on the heating rate. The thermal and kinetic values of the crystallization process were determined by analyzing the shifts of exothermal maxima in DSC thermograms depending on the heating rate. The Activation energy plots, for both steps of crystallization according Ozawa The Activation energy plots, for both steps of crystallization according KissingerStepEa[kJ/mol]OzawaEa[kJ/mol]Kissingerk[1/s]t1/2[1/s]1 445.5 11 433.1 11 0.01936.5 2 554.9 11 543.5 11 0.02330.1 The thermal and kinetic parameters process of crystallization The thermal and kinetic parameters process of crystallization It is obvious that initial sample, a, pass through successive phase transformations during heating treatment. Between ambient temperature and 300 C, initial alloy retains amorphous properties what is consistent with SEM investigations. Prolonged heating between 400 and 500 C induces amorphous alloy crystallization to, at least, two unidentified intermediary crystalline phases, (curves b and c). One of these two phases with characteristic peak at 2 =44.20, is more abundant and represent the (111) inter-planar distance of Co-rich FCC cubic crystal lattice. The phase is always present at 400 C, b, which means that its crystallization from amorphous matrix started earlier between 300 and 400. In other words, thermally induced elemental segregation in amorphous ribbon always starts in aforementioned temperature region. The alloy segregation/crystallization processes induced by heating are monitored also by appearance of dendritic forms in SEM micrographs taken between 400 and 500 C. References [1] J.D. Bernal, Nature, 185 (1960) 68. [2] S. Takayma, J. Mater. Sci., 11 (1976) 164. [3] U. Köster and U. Herald, Crystallization of metallic glasses, Springer, New York, 1981, p.225-259. [4]R.G. Garvey, Powder Diffr. 1(1986) 114. [5]. S. Krumm, Materials Science Forum, 228-231 (1996) 183. [6]. Joint Commity for Powder Diffraction Standards, file cards No. 15-0806 and 5-0727. a) c) a) b) c) d) SEM micrographs of thermally induced phase evolution of amorphous Co70Fe5Si10B15 alloy: a) the initial non-heated alloy; b) the initial alloy heated at 400oC for 20 minutes; c) the initial alloy heated at 700oC for 20 minutes; d) the initial alloy heated at 1000oC for 20 minutes. A whole range XRD powder pattern of Co70Fe5Si10B15 alloy after heating at 1000oC for 20 minutes. Thermally induced phase evolution of a) the amorphous o70Fe5Si10B15 alloy with temperature increasing: a) the initial alloy at ambient temperature; b) the initial alloy heated at 400oC for 20 minutes; c) the initial alloy heated at 500oC for 20 minutes; d) the initial alloy heated at 600oC for 20 minutes; e) the initial alloy heated at 700oC for 20 minutes.