Fe74.5-xCuxV3Si13.5B9 as-spun ribbons prepared by melt-spinning technique

Fe-Cu-V-Si-B nanocrystalline ribbons can be prepared using a melt-spinning technique without annealing processes. An appropriate addition of Cu improves the nucleation of α-Fe(Si) in as-spun Fe74.5-xCuxV3Si13.5B9 ribbons. There is an optimal Cu content, about x=2.5, for obtaining largest permeability and lowest magnetostriction in as-spun Fe74.5-xCuxV3Si13.5B9 ribbons. The permeability value (about 2.4x104) of as-spun Fe72Cu2.5V3Si13.5B9 (x=2.5) is much larger than that of Fe73.5Cu1V3Si13.5B9 annealed ribbons, due to the grain size of α-Fe(Si) for the former (12 nm) smaller than the later (41 nm). The smaller grain size of α-Fe(Si) for as-spun ribbon Fe72Cu2.5V3Si13.5B9 may be attributed to the refinement effect of Cu and the effect of high wheel speed in melt-spinning processes. Meanwhile, we have suggested that the capability of an element expelled from α-Fe(Si) and partitioned in the remaining amorphous phase is connected with the refinement of α-Fe(Si) grains. Based on Darken-Gurry solid solubility model, we have derived that the grain size of α-Fe(Si) reduces in order of Ta > Nb > Mo > W > V > Cr, which agrees to the experimental data very well. In addition, the DO3 ordered superstructure of α-Fe(Si) is observed in as-spun Fe74.5CuxV3Si13.5B9 ribbons, however it seems that the ordered degree of α-Fe(Si) grain is not a criterion for obtaining strong soft magnetic properties. (author)