Nanocrystallisation of an Fe_44.5Co_44.5Zr₇B₄amorphous magnetic alloy

The crystallisation of amorphous Fe44.5Co44.5Zr7B4 was investigated using DSC, electrical resistivity, TEM, HRTEM, CBED and VSM. Melt-spun amorphous Fe44.5Co44.5Zr7B4 crystallised by the primary crystallisation mode: the DSC results showed two exothermal peaks during heating. The electrical resistivity dropped sharply during the crystallisation event, which was consistent with DSC characterisation. From TEM, HRTEM and CBED results, primary crystallisation products which appeared to be clusters of crystals were found to be single crystal precipitates; these crystals formed in a compact dendritic morphology. Direct measurement of nucleation density and volume fraction was carried out using TEM analysis. The nucleation density was found to be high even in the absence of copper addition. The crystal growth was slow when the average size reached around 30 nm; this resulted in a stable nanocrystalline structure. The soft magnetic properties were improved after nanocrystallisation, the magnetic properties were related to the crystalline volume fraction and the Herzer model.