An analytical approach and experimental confirmation of dislocation–twin boundary interactions in titanium

Abstract

The morphology of $\{ 10\overline{1} 2\} \left\langle {\overline{1} 011} \right\rangle$ deformation twins formed in commercial purity titanium during an initial pass of equal-channel angular pressing was studied by transmission electron microscopy (TEM). The corresponding diffraction patterns show a symmetry line splitting of $(10\overline{1} 2)$ twin boundaries (TB) which is related to the presence of interfacial defects. A simple modeling for the interaction between non-screw a-slip lattice dislocations (Burgers vector b = $\frac{1}{3}[\overline{1} \overline{1} 20]$) and the $(10\overline{1} 2)$ twin plane is used according to crystallographic geometry and vector conservation. The results show that dislocation dissociation into different Frank partial dislocations on the interfacial plane is more favorable than its transmission to the other side of the interface. The formation of the Frank partials at the TB can produce a small change in the TB misorientation angle and this is consistent with the symmetry line splitting of the $(10\overline{1} 2)$ twin boundaries observed by TEM.