Twinning in nanocrystalline materials

The deformation twinning of nanocrystalline materials is analyzed within the dislocation theory of twins. This approach is used for the description of the recently observed inverse grain size effect in nanocrystalline face-centered-cubic metals. The analytical expressions are obtained for the grain size corresponding to the peak of the twinning propensity, the requisite external stress for twinning propagation in polycrystals and the grain size at which the slip begins to prevail over the twinning. The theoretical results are compared with the experimental data for twinning in Ni and Cu, and given predictions for Al.

► The inverse grain size effect in Ni and Cu is considered using dislocation theory.
► The twin growth stage of the deformation twinning in nc materials is analyzed.
► The theoretical results are compared with the experimental data for twinning.
► Given predictions the inverse grain size effect for Al.