Crystallization kinetics of the (Fe50Co50)73.5Ag1Nb3Si13.5B9 amorphous alloy

The crystallization kinetics of the (Fe50Co50)73.5Ag1Nb3Si13.5B9 amorphous alloy was studied using ferromagnetic resonance (FMR) measurements on samples annealed at 693 K for several periods of time and differential scanning calorimetry (DSC) measurements using several heating rates between 5 and 30 K/s. The increase of the FMR linewidth with annealing time is attributed to crystallization. Assuming a linear relation between the linewidth increase and the transformed volume fraction, it is possible to determine the Avrami exponent, n, from the FMR results: n=1.83±0.10. The DSC measurements show two exothermal peaks, suggesting a crystallization process involving more than one phase. The Avrami exponents calculated from the DSC measurements are n=1.80±0.10 for the first peak and n=1.50±0.10 for the second peak; these results are consistent with a diffusion-controlled process with a decreasing nucleation rate for the first peak and with a nucleation rate close to zero for the second peak. There is a reasonable agreement between the FMR results and the DSC results for the first peak. The activation energies are 353.5±2.8 and 424.9±10.2 kJ/mol for the first and second peaks, respectively.