Crystallisation progress in Si-rich ultra-soft nanocomposite alloy fabricated by melt spinning

Abstract The crystallisation process and the ultras-soft magnetic properties of amorphous/nanocomposite alloy Fe 73.5 Si 17.5 B 5 Nb 3 Cu 1 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 α - Fe ( Si ) started at 535 ∘ C . Further heating the sample leads to a transformation from the α - Fe ( Si ) to Fe - B phases at 670 ∘ 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 α - Fe ( Si ) nanocrystallite with mean size of 12.5 nm embedded in an amorphous matrix. At a volume fraction of 86% of α - 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 ∘ C in 40 min.