Chemical diffusion in ZrNb system

Abstract

The temperature and concentration dependence of interdiffusion coefficients in zirconium-niobium system has been established in the temperature range between 1593 and 1993 K by employing an electron probe micro analyser. The interdiffusion coefficients are found to increase with increase in zirconium content in the alloy and can be described by the relation D ̃ (C) = A (T) e 5.6C Here, A( T ) is the temperature dependent parameter and has the value of tracer diffusion coefficient at infinite dilution. C is the mole fraction of the component. The temperature dependence of interdiffusion coefficients can be represented by the Arrhenius expression of the type D ̃ (C) = D ̃ A 0 e Q ̃ /RT The activation energy ( Q ̃ c ) and frequency factor ( D ̃ 0 ) values in the composition range between 5 and 90% Zr lie in the range of 216 to 276 kJ/mol, and 10 −7 to 10 −5 m 2/s, respectively. An attempt has also been made to evaluate the impurity diffusion data by using interdiffusion values.