Abstract:

Structure, magnetic properties and ductile of melt-spun Fe_83-xSi₄B_13-yC_yCu_x (x = 0-1.7; y = 0-8) alloys were investigated. The addition of 1.7 at.% Cu in a Fe₈₃Si₄B₁₃ amorphous alloy generates abundant α-Fe crystals by providing nucleation sites, and further C doping promotes the growth of the crystals by suitable turning amorphous-forming ability, hence they increase saturation magnetic flux density (B_s) and slightly worse magnetic softness of the as-spun alloys. The as-spun Fe_81.3Si₄B₇C₆Cu_1.7 alloy possesses a combined structure of a fully amorphous layer in wheel side surface and predominating nanocrystalline structure with gradually enlarged α-Fe crystal, whose average size and volume fraction are determined as about 12 nm and 32%, respectively, therefore superior soft magnetic properties and ductile with a high B_s of 1.74 T, coercivity (H_c) of 32.7 A/m, effective permeability (μ_e, at 1 kHz) of 3200 and high relatively strain at fracture (ε_f) of 3.61% can be achieved directly in this alloy by only using melt-spinning. The annealing at 578 K releases internal stress, promotes the growth of the α-Fe crystals and remains the amorphous layer of the Fe_81.3Si₄B₇C₆Cu_1.7 alloy, then improves the soft magnetic properties and maintains the superior ductile with increasing the B_s and μ_e to 1.80 T and 14,100, respectively, lowering the H_c to 9.4 A/m and slightly reducing the ε_f to 2.39%. The combination of superior soft magnetic properties and ductile and simplified synthesis process entitles the Fe-Si-B-C-Cu nanocrystalline alloys great potentials in high performance electromagnetic applications.

Key words: Fe-based nanocrystalline alloys, High saturation magnetic flux density, Direct synthesis, Melt-spinning, Ductile