Low angle grain boundary diffusion of Cr in Nb bicrystals

Abstract

Grain boundary diffusion of Cr in [10]/[112] symmetrical bcc bicrystals of Nb has been investigated in the temperature range from 950 to 1197°C with tilt angles, θ, from 2 to 21°. For 0·17°, the activation energy is independent of θ, with an average value of 181-2kJ mol⁻¹, which is about half of the activation energy of lattice diffusion. The grain boundary diffusion coefficients are greater than the lattice diffusion coefficients by five or six orders of magnitude and vary linearly with sin (θ/2), in agreement with the dislocation-pipe model. These conclusions are generally consistent with the findings in fcc bicrystals.