Single-phase diffusion study in β-Zr(Al)

The diffusion behaviour of Al and Zr was investigated in the β-Zr(Al) phase in the temperature range 1203–1323 K by employing single-phase diffusion couples of pure Zr/Zr–2.8 wt% Al. The interdiffusion coefficients show a small increase with increase in Al concentration and follow a quadratic compositional relation. The temperature dependence of the interdiffusion coefficients at various compositions was established. The activation energy for the interdiffusion coefficient decreases linearly with an increase in Al concentration. The intrinsic diffusivity of Zr is higher than that of Al in this phase field. The impurity diffusion coefficient of Al in β-Zr was determined by extrapolation of interdiffusion coefficients to limiting concentration of Al and it shows temperature dependence: DAlβ-Zr(cAl=0)=5.567−1.80+2.65×10−6exp[(−220.08±3.33) kJ/RT] m2/s. A correlation between the impurity diffusion coefficients of various impurities in β-Zr and the atomic radii of the impurity atoms has been established and can be presented by the relation: logDimpβ-Zr (m2/s)=−14.57±1.22+exp[(4.84±2.83)−(30.22±2.66)r (nm)].