N. Shiga et al., NANOCRYSTALLIZATION OF AMORPHOUS FE-ZR-B-CU ALLOYS AND LOW-FREQUENCY SOFT-MAGNETIC PROPERTIES, Materials transactions, JIM, 36(7), 1995, pp. 939-944
In nanocrystalline alloys reported to date, Fe-Zr-B(-Cu) alloys shows
the highest saturation magnetization (higher than Fe-B-Si amorphous al
loys), they are thus expected to be applied to power transformers used
at Bm = 1.3 similar to 1.4 T and f = 50 similar to 60 Hz. Usually the
y are expected to be used in high frequencies because of their excelle
nt permeabilities. The low frequency (50 Hz) magnetic properties of Fe
86ZrxB13-xCu1 nanocrystalline ribbons have been examined from the view
-point of application to power transformers. Core loss W-13/50 (1.3 T,
50 Hz) = 0.07 W/kg was observed in the annealed Fe86Zr5B8Cu1 alloy. M
agnetic induction B-1k (in a field of 1 kA/m) is 1.54 T for the same s
ample. In annealing Fe86ZrxB13-xCu1 (x = 5 similar to 7) amorphous all
oys, ultrafine bcc-Fe grains about 15 nm in size were obtained with re
maining stable amorphous phases. The stable amorphous phase makes the
grains very fine. The stability of the amorphous phase is related to t
he liquidus temperature T-L that was measured during cooling and solid
ifying of the molten alloy of each composition in a furnace. When the
grains grew during annealing, the amorphous phase changed its composit
ion to exhibit lower T-L and became more stable. The core loss W-13/50
shows the W similar to D-6 dependence in the range of D = 15 similar
to 25 nn. However, when the grain size was D = 8 nm, the core loss doe
s not show the D-6 dependence. The nanocrystalline Fe-Zr-B-Cu ribbons
shows poor ductility, which should be improved if the materials are to
be used in actual pole transformers.