Soft magnetic properties and corrosion resistance of Fe-Co-B-M (M=Nb, Ta and NbNi) metallic glasses

Fe-based metallic glasses (MGs) with good soft magnetic properties, high thermal stability combined with high corrosion resistance should have greatest potential for wide variety of applications. In this work, the effects of Nb, Ta and NbNi additions on the glass forming ability (GFA), thermal stability, magnetic properties and corrosion resistance of the as-spun Fe-Co-B-based amorphous ribbons have been investigated. The (Fe0.7Co0.3)(75)B21Nb4 and (Fe0.7Co0.3)(75)B21Ta4 MG possess the larger supercooled liquid region > 40 K, presenting a high GFA. Via appropriate adjustment of the Fe/Co content ratio (4:1), the glass transition temperature and onset crystallization temperature of the (Fe0.8Co0.2)(75)B21Nb4 MG reach up to 800 and 826 K, respectively, indicating the best thermal stability. All the amorphous ribbons show the soft magnetic properties identified by the coercivity < 1.3 Oe. Moreover, the (Fe0.8Co0.2)(75)B23Nb4 MG exhibits the good soft magnetic properties with a high saturation magnetization (M-s) up to 206 emu/g (1.92 T). Besides a positive role of Nb addition, the enhanced M-s can be attributed to the increased magnetic moment with substitution of Co by Fe, and the easy movement of magnetic domains induced by the decreased atomic packing density. In addition, the tested samples are all spontaneously passivated with a large passive region during electrochemical polarization measurement in the seawater solution. Especially, the (Fe0.7Co0.15Ni0.15)(75)B21Nb4 MG presents the optimal corrosion resistance with the most positive corrosion potential.