Electromigration effect in Fe-Al diffusion couples with field-assisted sintering

Abstract The electromigration effect in spark plasma sintering (SPS) (a.k.a. field assisted sintering) is quantitively analyzed in the Fe-Al diffusion couple system. In SPS, the samples are heated by a high applied voltage and electric current, which can lead to an electromigration effect. Finite element analysis is utilized to determine the voltage applied to the Fe-Al diffusion couple, which is found to be order of magnitudes smaller than the overall system voltage, indicating the electron wind force would be the dominant mechanism for electromigration in SPS. Additionally, the simulation suggests the temperature and current density distribution is uniform across the metallic diffusion couple, which makes quantitative measurement feasible. A mathematic algorithm that allows diffusivity and electromigration coefficients to be solved, is developed for the Fe-Al, where multiple intermetallic phases coexist. At temperatures below aluminum melting, Fe2Al5 is the single intermetallic phases formed in Fe-Al system, for which electromigration is negligible. At temperatures above aluminum melting, FeAl2, FeAl and α-Fe solid solution phases coexist. Among them, the electromigration effect is noticeable in FeAl phase and is significant in the FeAl2 phase. The corresponding electromigration enhancement constants are calculated.