A paper in the recent Nature Materials (via iMechanica):

In situ observation of dislocation nucleation and escape in a submicrometre aluminium single crystal

S H Oh et al

‘Smaller is stronger’ does not hold true only for nanocrystalline materials but also for single crystals. It is argued that this effect is caused by geometrical constraints on the nucleation and motion of dislocations in submicrometre-sized crystals. Here, we report the first in situ transmission electron microscopy tensile tests of a submicrometre aluminium single crystal that are capable of providing direct insight into source-controlled dislocation plasticity in a submicrometre crystal. Single-ended sources emit dislocations that escape the crystal before being able to multiply. As dislocation nucleation and loss rates are counterbalanced at about 0.2 events per second, the dislocation density remains statistically constant throughout the deformation at strain rates of about 10-4 s-1. However, a sudden increase in strain rate to 10-3 s-1 causes a noticeable surge in dislocation density as the nucleation rate outweighs the loss rate. This observation indicates that the deformation of submicrometre crystals is strain-rate sensitive.

Good quality videos of bubble raft models of dislocations and grain boundaries are hard to come by. Here are some that I managed to find:

  1. via Technorati I came across these two YouTube videos (I think the language is Polish).
  2. And, of course, googling brought me these two videos where dislocations are shown under tensile, compressive and shear stresses.

Unfortunately, I am not able to find any of these bubble raft videos of indentation online (which Prof. Suresh showed us in his talk at Department of Materials Engineering, IISc, Bangalore).

Have fun (and if you know of any videos, let me know)!