Microstructure and Phase Transformations in a Liquid Immiscible Fe60Cu20P10Si5B5 Alloy

This work presents a study of the microstructure formed in a liquid immiscible Fe60Cu20P10Si5B5 alloy during moderate cooling on a copper plate and melt-spinning. The alloy ingot was re-melted on a copper plate and observed while cooling using a mid-wave infra-red (MWIR) camera. The heating and cooling characteristics of the melt-spun ribbon were studied using differential scanning calorimetry (DSC). The morphology and chemical composition of the ingot as well as the melt-spun ribbon were analyzed using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The compositions of the ingot and the ribbon were investigated using X-ray diffraction (XRD). Mössbauer spectroscopic measurements showing the influence of adding Cu to the Fe–Si–P–B alloy were also analyzed.The IR images from the MWIR camera enabled direct observation and identification of the liquid state transformations of the alloy. The DSC trace of the melt-spun ribbon showed crystallization of the amorphous matrix and confirmed that high temperature transformations occurred when the alloy was in the liquid state. Observations of the microstructure of the ingot revealed crystalline surface fractal structures formed by the Fe-rich eutectic constituent and Cu-rich fcc spherical precipitates. The morphology of the precipitates indicated that the precipitates formed in the miscibility gap. The microstructure of the melt-spun ribbon is composed of an amorphous Fe-rich matrix and elongated Cu-rich fcc precipitates. The observations based on the study of the microstructure are supported by Mössbauer spectroscopy.