Soft Magnetic Properties of Nanocystalline Fe-Si-B-Nb-Cu Rod Alloys Obtained by Crystallization of Cast Amorphous Phase

Abstract

An amorphous alloy rod of 0.5 mm in diameter was produced for an Fe_72.5Si₁₀B_12.5Nb₄Cu₁ alloy by copper mold casting, though the maximum diameter of 1.5 mm for (Fe_0.75Si_0.1B_0.15)₉₆Nb₄ alloy decreased by the addition of 1 at%Cu and the decrease in B content. The amorphous alloy rod crystallizes through multi-stage exothermic reactions. The first exothermic peak is due to the precipitation of nanoscale bcc-Fe phase and the following exothermic peaks result from the transition of bcc-Fe+amorphous→bcc-Fe+Fe₂₃B₆+Fe₂B+Fe₃Si+Fe₂Nb. The bcc-Fe phase has a particle size of about 10 nm and its volume fraction is approximately 70% after annealing for 300 s at 883 K . The alloy rod consisting of bcc-Fe and amorphous phases exhibits good soft magnetic properties, i.e., high saturated magnetic flux density of 1.21 T, low coercive force of 1.8 A/m and high initial permeability of 32000. The good soft magnetic properties for the nanocrystalline Fe_72.5Si₁₀B_12.5Nb₄Cu₁ alloy in a rod form of 0.5 mm in diameter are encouraging for future development as a new type of nanocrystalline soft magnetic bulk material.