The initial stage of nanocrystallization in Fe-Cu-Nb-Si-B ferromagnetic alloys

The reversible and irreversible heat flow phenomena during the pre-crystallization relaxation process of amorphous Fe73.5Nb3Cu1Si13.5B9 alloy have been studied. The pre-crystallization and the initial stages of crystallization with the redistribution of the elements of a rapidly quenched alloy were studied using differential scanning calorimetry (DSC), thermomagnetic analysis (TMA), Mossbauer spectroscopy (MS) and X-ray diffraction (XRD). MS allowed us to detect the beginning of the formation of Fe-deficient areas as iron-rich nanocrystals were appearing. The peak at 5 T hyperfine field value was found to appear when the samples were annealed at 733 K. This effect corresponds to Fe-deficient areas, and, probably to Cu-enriched cluster, as well. On the basis of this detailed research we discuss the model of decomposition of the amorphous phase with the subsequent formation of iron-enriched nanocrystals.