The influence of heat treatment on the microstructure and magnetic properties of (Fe,Co)-Zr-(Pr,Dy)-B- nanocomposite alloys

The microstructures and magnetic properties of rapidly solidified Fe61Co13.5Zr1Pr4.5-xDyxB20(x=0,1) alloys in the form of 1 mm diameter rods, 3 mm o.d. tubes and ∼150μm thick ribbon samples in as-cast state and as function of annealing temperature are reported and discussed. It is shown that the magnetic parameters of the annealed bulk samples are inferior to those of corresponding ribbon due to the presence of crystallites in as-cast state, in contrast to the fully amorphous structure for the ribbon samples. The structural differences were verified by the transmission electron microscopy. For bulk samples, a heterogeneous microstructure consisting of the large crystallites ∼300nm dia. deriving from the pre-existing nanocrystallites in as-cast state, and regions of nanocrystals of dia. <10nm deriving from the glassy phase was obtained on complete devitrification.