NANOCRYSTALLINE FE-M-B-CU (M=ZR,NB) ALLOYS WITH IMPROVED SOFT-MAGNETIC PROPERTIES

The soft magnetic properties of the nanocrystalline Fe-M-B (M=Zr,Nb) a lloys, which exhibit a high saturation flux density (B-s) above 1.5 T as well as a high effective permeability (mu(e)) above 30 000 at 1 kHz , were found to be improved by adding small amounts of Cu and by optim izing the chemical composition. The addition of Cu to the alloys decre ases the bcc grain size. The excellent soft magnetic properties (a hig h mu e of 100 000 at 1 kHz combined with a high B-s of 1.53 T) can be achieved in the region where small grain size, as well as nearly zero- magnetostriction are obtained, which is attained in the compositional range around Fe84Nb3.5Zr3.5B8Cu1. The soft magnetic properties can be further improved by low temperature annealing before the crystallizati on treatment. probably as a result of a decreased grain size distribut ion in the crystallized state. Consequently, the mu(e) reaches the max imum value of 120 000 for the nanocrystalline Fe84Nb3.5Zr3.5B8Cu1 allo y. (C) 1997 American Institute of Physics.