In this paper, the results of the investigation into the fractured surface microstructure of the amorphous samples of Fe36Co36B19Si5Nb4 in the shape of rods of diameters: 1 mm, 2 mm and 3 mm in the as-cast state are presented. The samples were prepared by injection of molten alloy into cooled copper dies. The process of diffusion in the investigated material has a different speed depending on the temperature gradient within the volume of the rod. The atomic diffusion leads to the creation of different zones within the rod fracture: the zone in contact with the copper die, the intermediate fracture zone, and the zone in the vicinity of the rod core; the three zones have been found to exhibit different amorphous structures.
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