In-situ thermomagnetic behaviors of an FeCuNbSiB alloy during nanocrystallization processes

An in-situ method was used to study thermal magnetic behaviors of cores mad e of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy, by recording the temperature dep endent initial permeability (mu(i)) in a designed thermal-cycling annealing . The higher the isothermal annealing temperature (T-IA) the shorter the ac cumulative time (t(Acc)) is required to attain the highest room temperature initial permeability (mu(ri.RT)), e.g., 61.39 ks for the T-IA at 520 degre es C, while 70 s at 600 degrees C. At a specific T-IA-t(Acc) combination, t he mu(i) value was found to be enhanced anomaly all the way down to room te mperature from a high annealing temperature. The composition effect, in par ticular the evolution of Si content in the nanocrystal during annealing, ha s also been studied and related to the observed permeability peak. The Curi e temperatures (T-c) of the nanocrystal and the residual amorphous phase we re found to dominate the mu(ri.RT) value, which was found to vary linearly and inversely with T-c of the residual amorphous phase in the annealed spec imen. The best results obtained from the current method is comparable with those obtained by conventional annealing via iteration, the thermal-cycling is thus an effective, time-saving and informative method to work out the b est process-annealing schemes for a specific composition, particularly a ne w one.