On the basis of a new model for basal slip in sapphire, the formation of a basal twin was considered. It was shown that deformation twinning was a natural prediction of the present slip model when the material was deformed in a particular regime of temperature and stress. The model was based upon the glide of a leading partial dislocation on a basal slip plane, with double cross-slip to the next-but-one slip plane. The model predicted the appearance of a type-II twin; that is, a twin that was related to the matrix by a 2-fold axis along the direction of shear, [10•0>, and lying in the twin/matrix interface.

P.Pirouz, B.F.Lawlor, T.Geipel, J.B.Bilde-Sørensen, A.H.Heuer, K.P.D.Lagerlöf: Acta Materialia, 1996, 44[5], 2153-64