AGING BEHAVIOR OF THE MICROSTRUCTURE AND SOFT-MAGNETIC PROPERTIES IN AMORPHOUS FE-SI-B-NB ALLOYS

The crystallization behaviors of amorphous Fe82Si6B10Nb2 and Fe79Si6B1 0Nb5 alloys were investigated using differential scanning calorimetry (DSC), transmission electron microscopy, and soft magnetic measurement s. The peak morphology of the DSC curve was significantly different be tween the two alloys, which suggests that their amorphous structures a re essentially dissimilar. The formation of a large amount of the dend ritic alpha-Fe phase with a grain size of 0.2-0.3 mu m was caused by a ging the former alloy for 0.6 Ms at 573 K, which leads to a marked inc rease in the coercivity as well as a decrease in the effective permeab ility mu(e). However, the notable enhancement of mu(e) was achieved up on aging below 623 K for the latter alloy, despite the fact that no cr ystallization occurs during the prolonged aging for 0.6 Ms. Whereas th e mu(e) at 1 MHz attained a maximum value of 2700 at 573 K, the aging at the first crystallization temperature for 3.6 ks resulted in a decr ease in mu(e) to 1650, which indicates the formation of nanoscale alph a-Fe particles. Such a difference in the crystallization behaviors bet ween the two alloys was reasonably interpreted within the framework of the structural model for amorphous Fe-Si-B alloys. (C) 1996 American Institute of Physics.