New FeNbB-based bulk amorphous and nanocomposite soft magnetic alloys

This paper deals with results on preparation and magnetic characterization over a wide frequency range of (Fe,Co,Ni)₇₀Nb₁₀B₂₀ new bulk amorphous and nanocomposite alloys. Their structure is either fully amorphous or consisting of very fine 5-10 nm α-Fe(Co) particles dispersed within the amorphous matrix. Saturation inductions of about 0.85 T, relative permeabilities of 7×10⁴ (at 80 Hz), and coercive fields of 40 A/m are determined for new Fe-Nb-B-based bulk amorphous torroids, whereas in nanocomposite cast bars, H_c varies between 180 and 360 A/m in the as-cast state and decreases by about half when the refined nanocrystalline structure is achieved. In the frequency range 50 Hz to 2 kHz, magnetic permeability decreases from 7×10⁴ to 0.5×10⁴. The potential impact of these materials on engineering applications is presented in connection with their specific magnetic behavior and casting ability.