High temperature soft magnetic properties of (FexCo1-x)73.5Cu1Mo3Si13.5B9 (x=0.5,1) alloys

The microstructure and high-temperature soft magnetic properties of amorphous and nanocrystalline (FexCo1-x)(73.5)Cu1Mo3Si13.5B9 (x=0.5,1) alloys were investigated. By substituting Co for Fe partially, the onset temperature of primary crystallization, T-x1(0) , for precipitating alpha-FeCo soft magnetic phase was decreased from 505 to 460 degrees C, while the Curie temperature of amorphous alloy, T-C(A)*, was enhanced from 320 to 455 degrees C. XRD patterns showed that a single alpha-FeCo crystalline phase with grain size about 16 nm was precipitated from amorphous matrix for (Fe0.5Co0.5)(73.5)Cu1Mo3Si13.5B9 alloy annealed between 460 and 580 degrees C. Although, the room temperature permeability of nanocrystalline (Fe0.5Co0.5)(73.5)Cu1Mo3Si13.5B9 alloy was not as high as that of nanocrystalline Fe73.5Cu1Mo3Si13.5B9 alloy due to a large saturation magnetostriction (>40 ppm), the improved high-temperature magnetic softness was observed for nanocrystalline (Fe0.5Co0.5)(73.5)Cu1Mo3Si13.5B9 alloy. The initial permeability about 1000 at 10 KHz can be maintained up to 600 degrees C, exhibiting a good thermal stability and higher initial permeability at elevated temperatures which is superior to that of Co-free Fe73.5Cu1Mo3Si13.5B9 alloy. The origin of this magnetic softness at elevated temperature was analyzed in terms of Hernando's enhancement effect theory of Curie temperature. (C) 2012 Elsevier B. V. All rights reserved.