The occurrence of serrated [101-2] twin interfaces in zirconium and titanium

The results of a study on the occurrence of serrated [101-2] twin interfaces in zirconium and titanium indicate that these serrations form on planes containing the twinning shear direction. During twin growth these serrations occur preferentially at the interface corresponding to the prominent corner produced at the free surface by the twinning shear. The occurrence of serrations is favoured, however, when the twinning shear results in a relatively small amount of surface tilt. When the surface tilt is relatively large, well-formed serrations in [101-2] twin interfaces occur less frequently since they cannot be easily accommodated. It is proposed that the ease with which the deformation modes of these h.c.p. metals accomodate the serrations is an important factor in determining the conditions that favour the occurrence of serrations. This proposal would also explain why the occurrence of serrated twin interfaces is principally a surface phenomenon. (Auth.)