Kinetic study of non-isothermal crystallization in Fe 78Si 9B 13 metallic glass

Abstract

This paper reports the differential scanning calorimetric (DSC) studies of metallic glass ribbon Fe 78Si 9B 13 at different heating rates. It is found that Fe 78Si 9B 13 metallic glass exhibits two-stage crystallization on heating. In order to calculate the activation energies for crystallization various thermal models are employed. The average values of the activation energies ( E c) were calculated and found to be 342 ± 10 and 351 ± 8 kJ/mol for the first and second phase, respectively. Kinetic parameters such as Avarmi exponent or reaction order ( n), dimensionality of growth ( m), and frequency factor ( K o) are also discussed. The reaction orders obtained for the two stages of crystallization were n 1 = 4 and n 2 = 5, confirming the bulk crystallizations of the samples. The deduced K o values for the two crystallization peaks are calculated to be 9.8 × 10 18 and 4.6 × 10 18 s −1. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques are used to identify the crystallized phases and morphology of the annealed samples, respectively. Rietveld X-ray profile fittings are also performed that revealed the obtained phases for the Fe 78Si 9B 13 metallic glass were cubic α-Fe(Si) and tetragonal Fe 2B with volume fraction of 44% and 56%, respectively.