Nanocrystallisation of amorphous alloys: comparison between furnace and current annealing

The mechanism of nanocrystallisation of the amorphous Fe72Cu1Nb4.5Si13.5B9 alloy has been studied with particular attention to the early stages of crystallisation. The specimens have been nanocrystallised by furnace (FA) and current (CA) annealing and analysed by Mِssbauer spectroscopy. X-ray scattering, using the beamline 5.2L at Elettra Synchrotron Source, Trieste, has been carried out on the same FA and CA samples, as well as on a previously untreated sample current heated in situ. It is found that for the same amount of nanocrystalline phase, the crystallite size in CA samples does not differ significantly from that in FA samples. Analysis of the Mِssbauer spectra shows that in FA and CA samples the nanocrystalline grains consist of non-stoichiometric partially disordered Fe3Si phase, and that there is an indication of the presence of boron atoms in the nanocrystals of CA samples. This implies a lower segregation of boron atoms or of borides at the boundaries of nanocrystallites of CA samples and can be connected to their lower brittleness.