Thermal stability and magnetic properties of amorphous Fe-based alloys with significant supercooled liquid region

Fe62Co7NbxZr10-xB20 (x = 0-6 at.%), amorphous alloys can be synthesized by melt spinning. The Fe-based metallic glasses show a rather wide supercooled liquid region before crystallization. The maximum supercooled liquid region is as large as 78.7 K for the alloy containing 4 at.% Nb. The addition of 2-4 at.% Nb causes an extension of the supercooled liquid region and an improvement of the thermal stability. The crystallization of the Fe-based alloys takes place through a single exothermic reaction, accompanied by the simultaneous precipitation of more than three crystalline phases such as alpha-Fe, Fe2Zr and ZrB2. The necessity of atomic rearrangements on a long-range scale plays an important role in the retardation of the crystallization reaction, which seems to result in the increase in the thermal stability of the supercooled liquid. The Fe-based glassy alloys exhibit soft ferromagnetic properties. The replacement of Zr by Nb causes a monotonous decrease in saturation magnetization. The saturated magnetostriction of the Fe-based glasses exhibits a relatively low value. There is no large change in saturation magnetization with the annealing temperature while the coercive force is slightly lowered and soft magnetic properties are improved by annealing treatment below the crystallization onset temperature. The devitrification leads to a remarkable increase in both saturation magnetization and coercive force. (C) 2002 Elsevier Science B.V. All rights reserved.