Diffusion of iron in Mg₆₀Ni₂₅Nd₁₅ amorphous alloys with a wide supercooled liquid region

Impurity diffusion of ⁵⁹Fe in Mg₆₀Ni₂₅Nd₁₅ amorphous alloys with a wide supercooled liquid region has been investigated over the temperature range from 407 to 469 K. Concentration depth profiles of the radioisotope ⁵⁹Fe in Mg₆₀Ni₂₅Nd₁₅ supercooled liquid and amorphous alloy have been measured by an ion beam sputter-sectioning technique. The temperature dependence of the impurity diffusivity of Fe in Mg₆₀Ni₂₅Nd₁₅ supercooled liquid (446-469 K) and amorphous alloy (407-438 K) is expressed as respectively D(supercooled) = 2.0 × 10^-10 exp (-53.3 ± 3.5 kJ mol^-1/RT)m²s^-1 and D(amorphous) = 7.7 × 10³ exp (-164.0 ± 19.4 kJ mol^-1/RT) m² s^-1 The temperature dependence of Fe diffusivities in the supercooled liquid region is less significant than that in the amorphous phase; the activation energy for diffusion in the supercooled liquid region is much smaller than that in the amorphous alloy by a factor of 3. Such a temperature dependence is consistent with results of viscosity measurement.