Low core losses of nanocrystalline Fe–Zr–Nb–B soft magnetic alloys with high magnetic flux density

The soft magnetic properties of the nanocrystalline Fe–Zr–Nb–B alloys, which are mixed Fe–Zr–B alloy with negative magnetostriction and Fe–Nb–B alloy with positive one, have been investigated. The magnetostriction and the grain size of the Fe–Zr–Nb–B alloys show intermediate values between those of the Fe–Zr–B and Fe–Nb–B alloys. The soft magnetic properties are strongly affected by Zr+Nb amount and Zr/Nb ratio. The best soft magnetic properties have been obtained for the Fe85.5Zr2Nb4B8.5 alloy. The alloy shows a high permeability of 60 000 at 1 kHz, a high saturation magnetic flux density of 1.64 T and zero-magnetostriction, simultaneously. The alloy also exhibits a very low core loss of 0.09 W/kg at 1.4 T and 50 Hz, which is extremely lower than that of Fe–Si–B amorphous, and good thermal stability of the core loss. The nanocrystalline Fe–Zr–Nb–B alloy is therefore suitable for a core material for pole transformers.