Nanocrystallisation behaviour of Fe82Nb6B12 alloy

The influence of different heat treatments on the nanocrystallisation behaviour of Fe82Nb6B12 amorphous alloys was investigated using different techniques. The microstructural studies have been correlated with the results obtained by means of X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry analysis under magnetic field measurements (TGM) and vibrating sample magnetometry (VSM). Heat treatments in the exothermic temperature range cause a devitrification of the amorphous phase giving rise to ultrafine α-Fe particles embedded in an amorphous matrix. The amorphous phase shows an enhancement of the Curie temperature that should be due to compositional changes of the amorphous phase. From XRD, the mean crystallite size was evaluated to be around 10 nm and the values are in agreement with those obtained from the TEM. The lattice parameter of the α-Fe decreases owing to the decrease in Nb and B content in the precipitates on annealing. The unusual high value of Ea (5.5±0.2 eV) was attributed to a significant contribution of nucleation to the first exothermic event.