Transformations in liquid state and microstructure development in immiscible Fe60Cu20P10Si5B5 alloy

A five-component Fe₆₀Cu₂₀P₁₀Si₅B₅ immiscible alloy was arc-melt and melt-spun from various temperatures. The microstructure and chemical composition of the ingot and melt-spun ribbons were analyzed using scanning electron microscope SEM/EDS. The melt-spun ribbon was investigated by transmission electron microscope (TEM). The melting range of the alloy was investigated by means of differential thermal analysis (DTA) and for reference, the temperature change during free cooling of the alloy was controlled by pyrometer in the melt spinning device. Processing with the slow cooling rate produced the fractal surface structures formed by the Fe-rich regions and Cu-rich regions. The arrangement of the regions was characteristic for the liquid immiscible alloys. It was found that the microstructures of the melt-spun ribbons depended on the ejection temperature. The lower ejection temperatures resulted in the formation of the lamellar structures separated into Fe-rich and Cu-rich regions. This was due to rapid cooling within the miscibility gap. Ejection at higher temperatures, above the miscibility gap led to the formation of a uniform amorphous/crystalline composite.