Thermomagnetic gravimetry study of crystallization behaviour in amorphous Fe-Si-B-Nb alloys

The effect of the Nb content on the crystallization process of amorphous Fe84- xSi6B10Nbx alloys has been investigated using thermomagnetic gravimetry (TMG). In the TMG measurement, the sample weight was electronically zerobalanced, and then an apparent weight (AW) applied by placing a magnet beneath the sample pan. The heating treatment was carried out over temperature range between 373 and 1093 K, in order to detect the formation of a ferromagnetic crystallization-induced phase. The form of the TMG curve changed markedly in the vicinity of 2-3 at.% Nb. In the alloys containing less than 2 at.% Nb, a two-stage increase in AW was observed with increasing temperature, but only a single-stage increase occurred for the alloys containing more than 3 at.% Nb. On the basis of these results, it is inferred that the Nb content plays a key role in the structure of the amorphous phase, supporting our recent claim for a mechanism of nanocrystallization.