Structural and magnetic properties of amorphous and nanocrystalline Fe-Si-B-P-Nb-Cu alloys produced by gas atomization

摘要

Fe-Si-B-Nb-Cu alloy powders, with and without P additions, were produced by gas atomization. The particles smaller than 20 mm are fully amorphous, exhibiting good soft magnetic properties. The crystallization process was studied by differential scanning calorimetry, demonstrating that its kinetics changes dramatically with small variations in the composition. The (Fe0.76Si0.09B0.10P0.05)(97.5)Nb2.0Cu0.5 (at. %) alloy was annealed in the supercooled liquid region (480 degrees C) and at the first crystallization peak (530 degrees C). The structural characterization by means of differential scanning calorimetry, X-ray diffraction, and transmission electron microscopy provided information that explained the excellent soft magnetic properties. Annealing at 480 degrees C produced an amorphous relaxed structure with improved soft magnetic properties. At 530 degrees C, a two-phase material formed by nanocrystals with an average grain size of 16-17 nm embedded in an amorphous matrix was developed. Partial nanocrystallization increased the saturation magnetization from 139 to 144 emu/g and reduced the coercivity from 2.24 to 0.69 Oe. These results can be understood in terms of the algebraic contribution of both phases to the magnetization and the application of the random anisotropy model to nanocrystalline soft magnetic materials. (C) 2019 Elsevier B.V. All rights reserved.