New Fe-based bulk glassy alloys with high saturated magnetic flux density of 1.4–1.5 T

New Fe-based bulk glassy alloys with high saturated magnetic flux density (Bs) were synthesized in (Fe0.75B0.15Si0.1)100−xMx (M=Nb or Zr; 2–4 at.% Nb or 1 at.% Zr) systems by copper mold casting. The addition of such small amounts of Nb or Zr causes the appearance of the glass transition and supercooled liquid region before crystallization. The glass transition temperature (Tg) and crystallization temperature (Tx) increased with increasing Nb content and the more significant increase in Tx as compared with Tg resulted in a maximum ΔTx(=Tx−Tg) value of 50 K at 4 at.% Nb. The liquidus temperature (Tl) also shows a significant change with Nb content and the 4 at.% Nb alloy shows the lowest Tl of 1374 K. The highest Tg/Tl of 0.61 was obtained for the 4 at.% Nb alloy. The maximum diameter of the cast glassy alloy rod was 1 mm for the 2% Nb alloy and 1.5 mm for the 4 at.% Nb alloy. The Nb- and Zr-containing bulk glassy alloys exhibit good soft magnetic properties of 1.40–1.53 T for Bs, 2.8–3.7 A/m for coercive force and 14,400–17,300 for permeability at 1 kHz. The success of synthesizing the new Fe-based glassy alloys exhibiting simultaneously high glass-forming ability, a large supercooled liquid region and the lowest Tl as well as good soft magnetic properties combined with high Bs allows us to expect future progress as a new type of soft magnetic material.