Microstructure and properties of the in situ formed amorphous-crystalline composites in the Fe-Cu-based immiscible alloys

The paper presents microstructures and mechanical properties of the melt-spun Fe30Cu32Si13B9Al8Ni6Y2 and Fe44Cu18Si13B9Al8Ni6Y2 alloys. It was found that liquid phase separation of the initially homogeneous melt occurred due to a positive heat of mixing between two major elements. The microstructures of the melt-spun ribbons were composed of the Fe-rich amorphous and the Cu-rich crystalline phases. A significant effect of the melt ejection temperature and the chemical composition (Fe and Cu content) on microstructures of rapidly solidified alloys was revealed. The microstructures of ribbons melt-spun from the miscibility gap region were non-uniform. On the other hand the microstructures of ribbons melt-spun from homogeneous melt temperature region were composed of the spherical precipitates distributed within the matrix. Superior hardness values of the examined ribbons melt-spun from the same temperature were found for the alloy with higher iron content. An increase of the melt-ejection temperature in the homogeneous melt region resulted in hardness decrease in case of the Fe30Cu32Si13B9Al8Ni6Y2 alloy and its increase for the Fe44Cu18Si13B9Al8Ni6Y2 ribbons. (C) 2011 Elsevier B. V. All rights reserved.