Interdiffusion in α-Solid Solution of the Fe-Al System

Abstract

Interdiffusion coefficients of bcc α-solid solution of the Fe-Al system in the temperature range between 800° and 1200°C and the γ-loop concentrations have been determined from the diffusion penetration curves obtained by an electron probe microanalyzer.
The results show that the activation energy for interdiffusion in the disordered phase varies between 30 and 45 kcal/mol while it is about 70 kcal/mol in the ordered phase. The activation energy for the self-diffusion of Al in pure α-Fe or dilute α-solid solution is predicted to be about 40 kcal/mol. This suggests that Al atoms diffuse much faster than Fe atoms in bcc Fe lattice.
The γ-loop determined from the diffusion penetration curves is somewhat different from those determined by the previous workers. The α⁄α+γ boundary is found at higher Al concentrations, while α+γ⁄γ boundary at lower Al concentrations, than those determined by microscopic observations or thermal analyses.