The self-diffusion coefficients of the 63Ni tracer in the metallic glass were measured at 575 to 645K by using the secondary ion mass spectrometry. The values of the diffusion coefficients were measured on the so-called air- and wheel-sides of the ribbon, and were found to lie between 5.6 x 10-23 and 11.2 x 10-21m2/s. In quenched specimens, the diffusion was found to decrease considerably with increasing annealing time, until a well-relaxed amorphous state was reached. The diffusion coefficients in the relaxed state were found to be described by:

air-side:     D(m2/s) = 4 x 10-4exp[-2.14(eV)/kT]

wheel-side:     D(m2/s) = 8 x 10-3exp[-2.29(eV)/kT]

The time dependence of the measured diffusivity during structural relaxation was interpreted in terms of the elimination of excess free volume by quasi-vacancies annealing out at the specimen surface; leading to additional transport of tracer atoms. The activation enthalpy governing this relaxation process was estimated to be about 1eV.

Diffusion Coefficients of 63Ni in Fe40Ni40B20 Metallic Glass. A.K.Tyagi, M.P.Macht, V.Naundorf: Acta Metallurgica et Materialia, 1991, 39[4], 609-17

Table 79

Diffusion of Ti in Fe40Ni40B20