Excellent soft magnetic Fe-Co-B-based amorphous alloys with extremely high saturation magnetization above 1.85 T and low coercivity below 3 A/m

Extremely good soft magnetic properties of high saturation magnetization (Bs) above 1.8 T and low coercivity (Hc) below 5 A/m were obtained for (Fe1-xCox)83B16Si1 (x = 0.1–0.3) amorphous ribbons annealed at the temperature between Tx1-120 K and Tx1-40 K. Here Tx1 is the onset temperature of the first exothermic crystallization peak. The best characteristics were 1.86 T for Bs and 3 A/m for Hc at x = 0.2. There are no previous data on the melt-spun alloys with high Bs above 1.8 T and low Hc below 5 A/m and hence the present amorphous alloys are regarded as a novel good soft magnetic alloy with high Bs comparable to Fe-Si steels. Curie temperature (Tc) of the x = 0.2 alloy was above Tx1 (708 K), implying high thermal stability of magnetic characteristics. The saturated magnetostriction for x = 0.2 was about 32 ppm and the effective permeability at 1 kHz showed as high as 1.6 × 104. The high Bs can be attributed to the low metalloid content containing mainly B element which suppresses effectively the reductions of Bs and Tc among metalloid elements, as well as the optimum Co/Fe content ratio with the maximum magnetic interaction in conjunction with maximum atomic volume. Moreover, these alloy ribbons exhibited good bending ductility even after optimum annealing treatment, in addition to high Vickers hardness of about 1000 and improved corrosion resistance comparing with the corresponding Co-free alloy. The excellent soft magnetic amorphous alloys are promising for further extension as engineering soft magnetic materials. [Display omitted] •Amorphous (Fe0.8Co0.2)83Si1B16 alloy shows high Bs of 1.86 T and low Hc of 3 A/m.•The annealed alloys keep good bending ductility and high Vickers hardness.•The Tc of alloy is higher than its Tx1, and Bs shows high thermal stability.