The internal stresses induced by the strain gradients in an array of lattice cells delineated by low-angle dislocation boundaries are partially relieved by the creation of new low-angle boundaries. This is shown to be a first-order transition, the new boundaries having finite misorientations. The calculated misorientations both of the new boundaries and of the existing boundaries which provoke the transition agree well with observations.
Nabarro, F. R. N., & Wilsdorf, D. K. (1996). Nucleation of small-angle boundaries. Scripta Materialia, 35(11), 1331–1333. https://doi.org/10.1016/1359-6462(96)00300-4