In situ TEM observations of dislocation processes in iron-aluminides with 25 and 30 at.% aluminium

Thin single crystal foils of long-range ordered binary iron—aluminium alloys with 25 and 30 at.% aluminium have been tensile tested inside of a transmission electron microscope. The motion of dislocations has been recorded under full load at temperatures ranging from 300 to 970 K. These experiments yield information pertaining to: i) the activated glide planes; ii) the mode of glide (viscous versus jerky and planar versus cross-slip); iii) the dissociation of perfect dislocations into partials and the magnitude of the partial Burgers vectors; and iv) the widths and specific energies of the antiphase boundaries between the partial dislocations. The results are discussed with a view of elucidating the well-known anomalous, positive temperature dependence of the critical resolved shear stress of these intermetallic compounds between 500 and 780 K.