Single crystals were strained  in situ, along the c-axis, in a transmission electron microscope. An investigation was made of glide on the pyramidal planes at temperatures of between -150 and 400C. The super-dislocations were shown to dissociate into 2 super-partials, with c+a/2 Burgers vectors. They glided on type-I pyramidal planes, rather than on type-II pyramidal planes as in the case of macroscopic compression along the c-axis. This difference was suggested to arise from the reversal of the applied stress. Glide-softening took place, and was tentatively linked to intensive disordering on the slip plane. The most mobile dislocations were of 30º-type, and lay parallel to the second c+a/2 direction on the slip plane. The least mobile were dislocations, usually of heavily cusped 60º-type, which nucleated a high density of rows of loops. It was concluded that the critical resolved shear stress for type-I pyramidal slip was governed by the density of pinning points on the less mobile dislocations.

An in situ Transmission Electron Microscopy Study of Pyramidal Slip in Ti3Al: Geometry and Kinetics of Glide M.Legros, Y.Minonishi, D.Caillard: Philosophical Magazine A, 1997, 76[5], 995-1011