The mechanism of the anelastic X relaxation in the intermetallic compound Fe3Al

A new type of anelastic relaxation (the so-called X relaxation) in Fe-Al-C alloys and in particular in the intermetallic compound Fe3Al, with an activation energy of about 1.7 eV, has been recently reported in the literature. Different atomistic mechanisms were proposed to explain this phenomenon. In this paper we discuss our hypothesis of the X relaxation--the “diffusion under stress” of interstitial carbon atoms in the vicinity of vacancies--using computer simulations and internal friction experiments. The computer simulations show that in a high vacancy containing Fe-Al-C solid solution, carbon atom diffusion to nearby vacancies gives an additional internal friction peak (the “X peak”) at a higher temperature as compared with the Snoek peak in the same alloy.