Structure of melt-spun Fe–Cu–Si–B–Nb alloy

Highlights: ► We report formation of the amorphous-crystalline composites in Fe–Cu–Si–B–Nb system. ► We used liquid phase separation to obtain spherical crystalline precipitates. ► Significant effect of the melt ejection temperature was found. ► Relatively large supercooled liquid region was noticed. -- Abstract: The Fe62Cu10B19Si5Nb4 alloy, melt-spun from 1450 and 1520 °C, has been studied by means of X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Liquid phase separation into the Fe-rich and the Cu-rich melts, due to a positive heat of mixing between iron and copper, was confirmed. Microstructures of the melt-spun ribbons are composed of the Fe-rich amorphous matrix and the Cu-rich crystalline phases. Significant differences in morphology of the Cu-rich phase were noticed with the melt-ejection temperature. If the alloy was melt-spun from a homogeneous melt region temperature (1520 °C), the Cu-rich melt precipitated in situ during cooling through the miscibility gap, assuming a spherical shape. The XRD pointed out presence of the Cu-rich solid solution in both melt-spun ribbons. A presence of the amorphous phase was fully confirmed by exothermic peaks in the DSC measurements. The studies pointed out at importance of the melt-ejection temperature parameter affecting crystallization behaviour of the amorphous phase. Single-stage crystallization, typical for the Fe–Si–B–Nb metallic glasses was found only for the ribbon melt-spun from 1520 °C