Accelerated crystallization and phase formation in Fe40Ni40B20 by electric current assisted annealing technique

The effect of electric current assisted annealing was investigated in amorphous Fe40Ni40B20 melt spun ribbons in terms of manipulating the crystallization temperature and phase formation. A specific setup was developed, which allows to measure the sample temperature and the electrical resistance in-situ during the annealing process. By employing these simultaneous measurements, the shift of the crystallization temperature was evaluated by employing different electric current modes and current densities. It was found that the onset temperature for crystallization is shifted to lower temperatures when a certain threshold of electric current density is surpassed. Maximum temperature shifts up to 130°C were achieved using direct and alternate current modes, while in pulsed current mode the maximum shift was 100°C. Even though a noticeable change was observed in the crystallization temperature when an electric current is applied during annealing, the nucleated phases were found to be the same as in the samples annealed without current. The reasons for the observed behavior are discussed and compared to propositions found in the literature. It is concluded that the ‘‘hot spots’’ mechanism is in good agreement with the results obtained in this work.