DIFFUSION IN AMORPHOUS METALLIC ALLOYS, PARTICULARLY CO58FE5NI10SI11B16

Self- and Ta-182 diffusion coefficients measured on amorphous Co58Fe5N i10Si11B16 by means of the radiotracer technique in combination with i on-beam sputtering for specimen sectioning are reported. These data ar e used to exemplify the characteristic features of diffusion in metall ic glasses and to establish the diffusion mechanisms in these material s. It is found that in unrelaxed metallic glasses diffusion is control led by an indirect mechanism in which vacancies, present in supersatur ation, act as diffusion vehicles. By contrast, in the relaxed amorphou s state diffusion takes place via direct collective diffusion mechanis ms, ranging from thermally activated atomic displacement chains (big d iffusing atoms in densely packed matrices) to single-atom jumps into n eighbouring vacant space produced temporarily via thermal fluctuations (small diffusers in loosely packed matrices).