A SIMS INVESTIGATION OF IMPURITY DIFFUSION IN AMORPHOUS FE40NI40B20

The diffusion coefficients of Be and Si in the amorphous alloy Fe40Ni40B20 were measured in the temperature range 575-643 K by using the technique of secondary ion mass spectrometry (SIMS). The measurements were carried out on the pre-relaxed alloy specimens and the diffusion coefficients D were found to lie in the range 1.0 x 10(-23)-2.0 x 10(-20) m2 s-1. The temperature dependence of the measured diffusion coefficients was found to be Arrhenius in nature yielding the values of the activation energy Q as 2.16 +/- 0.19 eV atom-1 and 3.39 +/- 0.30 eV atom-1 for the diffusion of Be and Si respectively. The corresponding values of the pre-exponential factors (D0) were 9.4 x 10(-4.0 +/- 1.57) m2 s-1 and 7.0 x 10(5.0 +/- 2.42) m2 s-1. An overall comparison of all the available data on diffusion in amorphous Fe40Ni40B20 clearly shows that the previously reported correlations for the diffusion coefficient D, the activation energy Q, and the pre-exponential factor D0 for amorphous alloys are seen in this alloy also. It is suggested that the mechanism of diffusion possibly involves a cooperative movement of a group of atoms.