The equilibration of the thermal vacancy concentration in these B2-type materials was measured by applying positron lifetime techniques to a diffused 58Co positron emitter. It was found that the equilibration process occurred rather slowly; thus indicating a low vacancy mobility. The enthalpies of vacancy formation were equal to 1.04eV and 0.98eV, respectively, for Fe63Al37 and Fe61Al39. The enthalpy of vacancy migration was equal to 1.7eV in both cases.

Simultaneous Study of Vacancy Formation and Migration at High Temperatures in B2-Type Fe Aluminides. R.Würschum, C.Grupp, H.E.Schaefer: Physical Review Letters, 1995, 75[1], 97-100