An  in situ  transmission electron microscopic investigation was made of the dynamic behavior of dislocations on the type-I pyramidal slip planes of single crystals when specimens were strained in tension along the c-axis. It was found that super-partial dislocations split asymmetrically into 2 unlike partials. The high-energy complex stacking fault which was involved was thought to relax via short-range diffusion. This was suggested to account for a very marked disordering, glide softening, and nucleation of loops. Three loop families were identified, all of which were of vacancy type. Mechanisms were proposed in order to explain the formation of loops, their interaction with mobile dislocations, and their alignment along a c+a/2 direction which was different to the Burgers vector direction of the gliding dislocations. It was concluded that the critical resolved shear stress for pyramidal slip was governed by loop nucleation.

An in-situ Transmission Electron Microscopy Study of Pyramidal Slip in Ti3Al: Fine Structure of Dislocations and Dislocation Loops M.Legros, Y.Minonishi, D.Caillard: Philosophical Magazine A, 1997, 76[5], 1013-32