On the transition between the C and B kinetic regimes for grain-boundary diffusion

Abstract

It is shown that, in the transitional region between the B and C kinetic regimes for grain-boundary diffusion, the product of the grain-boundary width δ, the segregation factor K and the grain-boundary diffusion coefficient D ^b= KδD ^b), as well as the grain-boundary diffusion coefficient itself, can be estimated. From penetration plots measured at different annealing times in the transitional region (0.01 < α < 10, where α = Kδ/2(Dt)^1/2 is the relative grain-boundary width and D is the volume diffusion coefficient) by fitting with solutions in the B and C kinetic regimes, one can obtain the apparent values for P and D ^b. From the solution of the general problem of grain-boundary diffusion, correcting functions are given for the calculation of the true values of P and D ^b (and consequently of Kδ). This procedure is illustrated by several experimental examples published in the literature as measurements in the C kinetic regime.