Comparison of wagner’s relations for diffusivity determination in binary systems with moving joint boundary with the results of generalized theory

Abstract

Approximate Wagner’s relations for the diffusion description in semiinfinite systems with nonstationary interphase boundary are compared with the results of the exact solution of the problem. The cases of diffusion from phaseα into phaseβ and from phaseα into phaseα +β were taken into consideration. In dependence on the interphase boundary concentrations and direction of the boundary displacement, the results obtained from Wagner’s relations can differ only slightly from the results of the generalized theory. However, we can also encounter the cases when the differences are some hundreds of per cent. It is impossible to state a priori when Wagner’s solution is sufficiently exact and when the exact solution must be used for calculations.