Effect of minor additions on the glass forming ability and magnetic properties of Fe-Nb-B based metallic glasses

The glass forming ability, thermal stability, nanocrystallization, and magnetic properties of Fe(65-x)Nb(10)B(25-x) (x = 0,5,10), Fe(75+y)Nb(9-y)B(15)Cu(1) (y = 0,2,4) and Fe(77-z)Co(z)Nb(7)B(15)Cu(1) (z = 2,4,8) metallic glasses have been studied. The results show differences in the nanocrystallization changing from the metastable Fe(23)B(6) phase to bcc-Fe when increasing the relative Fe/B content. The ternary FeNbB alloys are good soft magnets in the glassy state and glass forming ability is enhanced with the B content. However, their nanocrystallization leads to large increase of coercivity. The (Fe,Co)-Nb-B-Cu alloys show bcc-Fe or bcc-(Fe,Co) grains with a refined microstructure (4-6 nm) after nanocrystallization with relatively low coercivity values (in the range 4-15 A/m). The replacement of Nb by Fe and the addition of Co enhance the values of both the Curie temperature and saturation polarization from 346 K to 493 K (for Fe(69)Co(8)Nb(7)B(15)Cu(1)) and from 1.0 T to 1.4 T (for Fe(79)Nb(5)B(15)Cu(1)), respectively. (C) 2009 Elsevier Ltd. All rights reserved.