Nanocrystallisation behaviour of Fe82Nb6B12 alloy

The influence of different heat treatments on the nanocrystallisation behav iour of Fe82Nb6B12 amorphous alloys was investigated using different techni ques. The microstructural studies have been cor-related with the results ob tained by means of X-ray diffraction (XRD), differential scanning calorimet ry (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 ri se to ultrafine alpha -Fe particles embedded hi an amorphous matrix, The am orphous phase shows an enhancement of the Curie temperature that should be due to compositional changes of the amorphous phase. From XRD the mean crys tallite size was evaluated to be around 10 nm and the values are in agreeme nt with those obtained from the TEM. The lattice parameter of the alpha -Fe decreases owing to the decrease in Nb and B content in the precipitates on annealing, The unusual high value of E-a (5.5 + 0.2 eV) was attributed to a significant contribution of nucleation to the first exothermic event. (C) 2001 Elsevier Science B,V, All rights reserved.