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

Abstract 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.