عنوان مقاله [English]
In the current study, nanocrystalline Finemet soft magnetic cores were processed and their thickness was improved by the hot pressing technique. Besides, the effect of hot pressing on the microstructure and soft magnetic properties of the amorphous precursor was compared with the conventional annealing method. First, amorphous Finemet ribbons were produced through the melt-spinning method. Thermal behavior of the amorphous Finemet ribbons and crystallization of the anocrystalline phase was studied by Differential Scanning Calorimetry. Thus, the proper crystallization temperature of the amorphous phase was specified about 550 ºC. To crystallize the nanocrystallime phase from the amorphous matrix, the produced ribbons were either annealed conventionally at 550 ºC for 30 min or hot pressed at the same temperature for 60 min, under a controlled H2/Ar atmosphere, a 30% H2, 70% Ar mixture. The formed phases were specified by X-ray diffraction, and microstructure of the formed alloy was evaluated by scanning electron microscopy. It was shown that, both methods result in the formation of α-FeSi nanocrystals embedded in an amorphous matrix. The average size of the formed α-FeSi nanocrystals was calculated by using the MAUD software, came out to be 17 and 12 nm, for annealed and hot pressed samples, respectively. Hence, hot pressing results in crystal size reduction, compared with the conventional annealing method. Moreover, this processing method can decrease the soft magnetic properties of the amorphous precursor. However, the produced cores exhibit good soft magnetic properties (Hc~ 8 Oe, σ~ 130 emu/g).