Effect of Cu, Nb and Si on the crystallization behavior and magnetic properties of Fe77Cu0.6Nb2.4Si11B9

Amorphous ribbons of composition Fe77Cu0.6Nb2.4Si11B9 have been annealed temperatures of 500, 520 and 5300C for 1 hour, which produces homogeneous, ultra-fine grain structure of about 11 nm on an average. The amorphosity of the ribbons has been confirmed by x-ray diffraction. Activation energy of crystallization of α-Fe(Si) and iron boride phase has been obtained as 2.02 and 3.66 eV respectively. Excellent correlation between initiation of crystallization temperature and volume fraction of crystalline phase of α-Fe(Si) has been obtained between differential thermal analysis and temperature dependence of magnetization. Crystalline volume fraction of α-Fe(Si) determined by differential scanning calorimetry has been found to be 77% at 5000C, 92% at 5200C and 97% at 5300C. Crystalline volume fraction of α-Fe(Si) determined by thermomagnetic measurements for samples annealed at 5200C for 1 hr. is about 93%. B-H loop of as-cast and annealed samples revealed that excellent soft magnetic properties develop after optimum annealing. (author)