It was shown that there existed a metastable arrangement of products in the reaction:

a<111>  a<110> + a<001>

in B2 NiAl. Atomistic calculations showed that the metastable state could be formed spontaneously by a local shuffle or climb decomposition. Once formed, the so-called pick-a-back configuration could glide as a unit; with a restoring force helping to keep it intact. However, if the product lines became separated locally by more than a critical distance, the result was a decomposition loop. Small dislocation loops (less than 10nm) collapsed, large loops (greater than 300nm) evolved into dislocation dipoles and medium loops could fail to evolve further. The results were consistent with detailed observations of microstructures.

The Mechanics of Slip Transition at Intermediate Temperatures in <001>-Oriented NiAl Single Crystals - II. A Metastable State for a<111>{110} Dislocations in NiAl and its Role in their Decomposition. J.Brown, R.Srinivasan, M.J.Mills, M.S.Daw: Philosophical Magazine A, 2000, 80[12], 2855-70