INITIAL MAGNETIC-PERMEABILITY DURING THE DEVELOPMENT OF THE NANOCRYSTALLINE STATE IN AMORPHOUS RIBBONS

Low-field initial permeability (mu(i)) has been measured at several st eps of nanocrystallization in four amorphous Fe73.5Cu1Nb3Si13.5B9 ribb ons produced by planar flow casting with different quenching rates (QR s) from the melt. It is observed that the increase in mu(i) upon nanoc rystallization is strongly influenced by the initial free-volume conte nt of each sample. Samples produced with higher quenching rates exhibi t a faster transformation kinetics and stronger enhancement of the ini tial permeability in the nanocrystalline state. Conventional heat trea tments and accumulative annealings were performed on all the ribbons, in order to study the effect of their inhomogeneities and induced anis otropies.