Using in situ transmission electron microscopy, the stability of growth twins was studied. The rapid migration of incoherent twin boundaries was observed, indicating that nanotwins were unstable. Topological analysis and atomistic simulations were adopted to explore de-twinning mechanisms. The results showed that: (i) the de-twinning process was accomplished via the collective glide of multiple twinning dislocations that formed an incoherent twin boundary; (ii) de-twinning could easily occur for thin twins, and the driving force was mainly attributed to a variation of the excess energy of a coherent twin boundary; (iii) shear stresses enable incoherent twin boundaries to migrate easily, causing the motion of coherent twin boundaries; and (iv) the migration velocity depends on stacking fault energy. The results imply that de-twinning becomes the dominant deformation mechanism for growth twins of the order of a few nanometers thick.

Detwinning Mechanisms for Growth Twins in Face-Centered Cubic Metals. J.Wang, N.Li, O.Anderoglu, X.Zhang, A.Misra, J.Y.Huang, J.P.Hirth: Acta Materialia, 2010, 58[6], 2262-70