The dynamic behavior of dislocations on so-called easy slip systems was studied by means of in situ straining experiments in a high-voltage electron microscope. At high temperatures, the dislocations were smoothly curved (NiAl, TiAl) or sometimes exhibited super-kinks (MoSi2), and moved in a viscous manner. This suggested that the dynamic behavior, as well as the flow-stress anomaly, were related to the formation of atmospheres around the dislocations. A model was proposed which assumed that the lowest-energy configuration of a dislocation required a certain number of antisite defects or other point defects in the dislocation core. This cloud of disordered structure could then partially follow the moving dislocations and produce additional friction; analogous to other diffusion-controlled mechanisms. The concept of such atmospheres controlling dislocation mobility in intermetallics at high temperatures was supported by measurements of the dependence of the strain-rate sensitivity on the strain-rate itself.

Dynamic Dislocation Behavior in the Intermetallic Compounds NiAl, TiAl and MoSi2. U.Messerschmidt, M.Bartsch, S.Guder, D.Haussler, R.Haushalter, M.Yamaguchi: Intermetallics, 1998, 6[7-8], 729-33