Impurity diffusion of Al in β-Zr

The impurity diffusion of Al in β-Zr has been investigated in the temperature range of 1203 K to 1323 K. The interdiffusion coefficients have been determined by Hall's analytical method. The interdiffusion coefficients bear a linear relation with Al concentration of the type D =a+b CAl in the range 0≤ CAl ≤ 2at%. The impurity diffusion coefficients have been established by extrapolation of interdiffusion coefficients to limiting concentration of CAl→0. The impurity diffusion coefficients show an Arrhenius type of temperature dependence and can be described by : DAl(ca=0)βZr= 5.567-1.80+2.65 x 106exp [( -220.08±3.33)kJmol-1/RT] m2/s. The difference between the activation energies of impurity diffusivity of Al and self-diffusivity of Zr in β-Zr is 104.3kJmol-1. This positive difference in the activation energies indicates very low impurity-vacancy binding energy. The interrelation between the activation energy Q and the pre-exponential factor D0 of impurity diffusivity is discussed in perspective of Swalin's and Beke's theories. The values of the impurity diffusion parameters are in conformation with these theories. A co-relation between the impurity diffusion coefficients of DimpβZr various elements in β-Zr and their atomic radii (r) has been established and can be presented by the relation logDimpβZr (m2s-1)=-14.57 ±1.22+ exp[(4.84± 2.83) - (30.22±2.66)r(nm)] The impurity diffusion coefficient value of Al in is in conformation to this relation. (author)