In situ crystallization of metallic glasses during magnetic field annealing

The impact of an external magnetic field upon changes in the crystallization kinetics of Fe90Zr7B3 metallic glass is studied by in situ nuclear forward scattering (NFS) of synchrotron radiation. Structural and magnetic information on the whole process of nanograin formation is monitored on fly in real time by means of time domain Mössbauer effect technique. Isothermal annealing performed at 753 K under weak magnetic field (Bext = 0.652 T) exhibits more rapid crystallization in comparison with zero-field conditions. These surprising effects of an external magnetic field upon the process of phase transformation are attributed to energetic perturbations of magnetic interactions in comparison with the thermal energy. Consequently, the formation of nucleation centers is enhanced. Such accelerated crystallization was not reported so far for metallic glasses exposed to magnetic field during annealing. The influence of magnetic field on the resulting properties is usually assessed under static conditions after annealing. The use of NFS with rapid data acquisition has allowed in situ observation of the microstructure development throughout the fast annealing processes. In this way, not only the starting and the final stages of the structure can be characterized but also the intermediate transition period states of the transformation can be followed to fine details.

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