Phenomenological Consideration on the Compositional Deviation from Equilibrium at the <I>bcc</I>⁄<I>fcc</I> Interface in Fe: Cr Diffusion Couples

Abstract

The phase boundary compositions at the α⁄γ interface in γFe:Cr diffusion couples have been examined by electron microprobe. The results show that the boundary compositions deviate from equilibrium values. The compositional deviations are analyzed in terms of atomic mobility on the basis of the phenomenological theory of material transport. It is found that the atomic mobility in the transfer across the α⁄γ interface is less than that in the lattice diffusion in the α or γ phase by a factor of 10−2∼10−4. The reason for this low mobility in the transfer across the interface is considered to be due to a large negative value for the entropy of activation in the transfer process involved.