Transformation kinetics of the Fe73.5Cu1Nb3Si13.5B9 ribbons to the nanocrystalline state

On the isothermal kinetics analysis of transformations in metastable systems: combined use of isothermal and non-isothermal calorimetry

“…It has been shown that the isothermal annealing below the onset temperature of the nanocrystallization, T o , is not able to complete, in a reasonable time, the nanocrystallization process but a residual exothermic peak remains even for very long annealing times [7,24,25]. Consequently, the total fraction of transformation (normalized to 1) can not be obtained directly from the enthalpy released in the isotherm, because the process is only partially completed during this treatment.…”

The peculiarity of contraction in the primary crystallization of amorphous Fe73.5Nb3Cu1Si13.5B9 alloy

“…This is an interesting matter to investigate. It is known that the crystallization process of an amorphous alloy is controlled by the diffusion mechanism [13,14]. In the absence of interfacial instabilities the growth is parabolic with time, i.e., r (the crystallite radius) increases linearly with the square root of time.…”

Nanocrystallization kinetics of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy

“…These results can be applied to explain the variable E a and Avrami Table 2 Kinetic parameters of SB (m,n) model calculated from DSC data using Eqs. (8) and (9) Heating rate β ( exponents during crystallization of Finemet alloy presented in many papers [9][10][11][12][13][14][15][16].…”

“…In the studies on the crystallization kinetics of Finemet alloys, Johnson-Mehl-Avrami (JMA) kinetics equation (or JMA based equations) was generally assumed [8][9][10][11][12][13][14][15][16][17][18]. Although a number of papers relating to this have been published, an unique explanation is not reached yet.…”

“…For example, distinguishable values of activation energy E a (such as E a = 567, 479, 384, 360, 321, 143 kJ/mol) and a variable E a were obtained by differential scanning calorimetry (DSC) [9][10][11][12][13]. And some anomalous values of the transformation index (<1) or a large change in the index with crystallized fraction were observed [9,[14][15][16]. In order to explain these different results, several mechanisms have been suggested, e.g., the athermal nucleation [17].…”