Soft Magnetic Properties of bcc Fe-M-B-Cu (M=Ti, Nb or Ta) Alloys with Nanoscale Grain Size

The changes in microstructure and magnetic properties upon crystallization were investigated for melt-spun amorphous Fe-M-B-Cu (M=Ti, Nb or Ta) quaternary alloys. A mostly single bcc phase with nanoscale grain size of about 10 nm was formed by annealing the amorphous Fe-M-B-Cu alloys for 3.6 ks in the range of 750 to 950 K. The crystallization-induced bcc alloys were found to exhibit a high permeability (µ e ) of from 10000 to 20000 at 1 kHz, combined with a high saturation magnetization ( B s ) of from 1.40 to 1.55 T. These values are superior to those for amorphous Fe-Si-B alloys which are a known soft magnetic material with high B s .