The crystallisation process and the ultras-soft magnetic properties of amorphous/nanocomposite
alloy Fe73.5 Si17.5 B5 Nb3 Cu1 fabricated by conventional melt-spinning technique are systematically
investigated in terms of thermal analysis and in-situ measurement of magnetisation dynamics. The thermal
analysis using differential scanning calorimetry showed that crystallisation from Fe-based amorphous state
to ?-Fe(Si) started at 535 {ring operator} C. Further heating the sample leads to a transformation from the ?-
Fe(Si) to Fe-B phases at 670 {ring operator} C. Crystallisation activation energies were determined using
two models: Kissinger and John-Mehl-Avrami (JMA), which were consistent to each other with a value of
2.81 ? 0.03 eV. High resolution transmission electron microscopy investigation revealed an ultrafine
structure of ?-Fe(Si) nanocrystallite with mean size of 12.5 nm embedded in an amorphous matrix. At a
volume fraction of 86% of ?-Fe(Si) phase, optimum soft magnetic properties were obtained with very high
permeability of 110,000 and a very low coercivity of 0.015 Oe by annealing the amorphous alloy at 530
{ring operator} C in 40 min. Crown Copyright ?? 2009.
