Mesoporous surfaces were formed in B2-type FeAl single crystals by quenching into iced water, followed by surface treatments and an ageing heat treatment. The pore shape changes depending on surface orientation, because the surfaces of the mesopores were surrounded by {100} planes in the same way as mesopores observed inside rapidly solidified FeAl ribbons. The pore size seems to increase with increasing temperature of the aging heat treatment. Two relaxation peaks were observed in DSC thermograms, and the activation energy was estimated to be approximately 1.84eV for the peak in a higher temperature range. TEM observations suggested that the observed DSC peaks correspond to vacancy condensation and/or absorption by [100]-type dislocations. The experimental results also strongly suggested that the mesopore formation near surfaces was caused by the condensation of quenched-in, supersaturated thermal vacancies.

Surface Mesostructure Change of B2-Type FeAl Single Crystals by Condensation of Supersaturated Thermal Vacancies. K.Yoshimi, T.Kobayashi, A.Yamauchi, T.Haraguchi, S.Hanada: Philosophical Magazine, 2005, 85[2-3], 331-44