Mössbauer study of the surface barrier to the diffusion of iron into aluminum

A layer of iron was deposited on the surface of an aluminum sample and its diffusion into the aluminum was then studied by means of the Mössbauer effect in⁵⁷Fe. It was found that at high temperature the iron quickly combines with aluminum to form Fe₄Al₁₃, presumably in the form of a thin surface layer. The iron dissolves out of this phase and into the fcc solid solution very slowly at high temperature. This fact helps to account for the holdup of iron at the surface of aluminum as observed in tracer measurements of the diffusion of iron through aluminum.