Recent advances made concerning supersaturated vacancy behavior in rapidly quenched FeAl investigated by differential scanning calorimetry measurements coupled with transmission electron microscopic observations were reviewed. There were two exothermic peaks only at the first heating step of differential scanning calorimetry for the rapidly quenched FeAl. The first peak was small and lay in a lower temperature range, and the 2nd peak was large; lying in a higher temperature range. The apparent activation energy of the exothermic reactions changes not only with Al concentration but also with quenching temperature. This indicates that the apparent activation energy was not the material constant of FeAl but a variable that changes with the concentration of supersaturated thermal vacancies. The 2nd peak corresponds to the nucleation and growth of vacancy clusters and complexes inside the bulks due to the condensation and annihilation of supersaturated vacancies, i.e. the formation and growth of cuboidal voids for rapidly solidified ribbons and of <100>-type prismatic loops for water-quenched single crystals. The morphology of the vacancy complexes grown under the 2nd peak was correctly expressed by the Johnson–Mehl–Avrami equation extended by Matusita et al. for the differential scanning calorimetry curves: the morphology factor, m, nearly equals to 2 for the formation and growth of <100>-type prismatic loops and to 3 for those of cuboidal voids. Therefore, the extended Johnson–Mehl–Avrami method would be useful to judge the morphology of vacancy complexes.

Differential Scanning Calorimetry Study on Annihilation Behavior of Supersaturated Thermal Vacancies in B2-Type FeAl. K.Yoshimi, M.Tsunekane, K.Maruyama: Intermetallics, 2010, 18[7], 1265-72