Decomposition behaviour of amorphous Fe89−xZr7B3Cu1Gex alloys

Abstract

The decomposition behaviour and the effect of Ge on the microstructural evolution in Fe89−xZr7B3Cu1Gex (x = 0 and 3 at%) alloys were examined using differential scanning calorimetry, x-ray diffraction (XRD), transmission electron microscopy (TEM) and field emission scanning TEM with nanoprobe energy-dispersive x-ray spectroscopy (NanoEDXS). The onset temperatures of primary crystallization for amorphous Fe89−xZr7B3Cu1Gex alloys were found to be independent of the Ge content. The XRD and TEM results showed that the crystallization takes place through two stages of amorphous→bcc Fe+residual amorphous → α−Fe+Fe3Zr, regardless of Ge content. The addition of Ge has an effect on reducing the grain size of the Fe89Zr7B3Cu1 alloy by 10–15%. The NanoEDXS results confirmed that Ge is enriched in the residual amorphous matrix together with Zr, resulting in enhanced Curie temperature and the exchange stiffness of the intergranular region. The refined grain size and the partitioning of Ge into the intergranular region together resulted in improved soft magnetic properties. Further, the NanoEDXS results implied that unlike Cu, Ge does not assist in the heterogeneous nucleation of the bcc Fe phase during the primary crystallization reaction.