Single-curve multivariate kinetic analysis: Application to the crystallization of commercial Fe-Si-Cr-B amorphous alloys

Abstract

Crystallization behavior of three commercial Fe-Si-Cr-B amorphous alloys (AFSC, SAP-2KC and AW2-08) was investigated by means of differential scanning calorimetry, optical and scanning electron microscopies, and X-ray diffraction analysis. The complex crystallization kinetics was described using the transformation mechanism of multiple overlapping independent processes following the autocatalytic Sestak-Berggren model. Kinetic parameters of this reaction scheme were determined using the newly developed method of single-curve multivariate kinetic analysis (sc-MKA). Accuracy of the kinetic predictions made by this method was confirmed via combined experiment consisting of low-temperature isothermal annealing followed by non-isothermal scan. The sc-MKA method accurately predicted the degrees of conversion achieved during the annealing. In addition, for AFSC and SAP-2KC the method also very well predicted the actual complex growth rate occurring during the consequent heating. Merits of the combined iso-/nonisothermal temperature programs were discussed with respect to the unexpected conversion-dependent change of crystallization kinetics found for the AW2-08 amorphous alloy.