Diffusion of PdCuNiP alloys from the amorphous to the liquid state

Interdiffusion in molten PdCuNiP alloys above the melting temperature and impurity diffusion in Pd₄₀Cu₃₀Ni₁₀P ₂₀ above and below the glass transition were investigated. For the interdiffusion measurements in the liquid alloys capillary methods were used in the temperature range from 973 to 1373 K. Uphill diffusion was observed for Pd and P in the presence of chemical gradients of Cu and Ni, respectively. This result correlates with mixing enthalpies calculated for the partial ternary systems. The measured temperature dependence of the interdiffusion coefficients is in accordance with the prediction of the mode coupling theory (MCT). The temperature dependence of the impurity diffusion coefficients in the non-relaxed glass shows "non-linear" Arrhenius behaviour with a kink near the glass transition. After long time relaxation at temperatures well below the glass transition the coefficients follow an uniform Arrhenius dependence over the entire temperature range with reduced diffusion coefficients below the glass transition.