Screw Dislocations as Nucleation Centers of Twinned ε-Martensite Crystals with {443}α Habits in Titanium

Abstract

The formation of twinned crystals with habits close to {443}_α in titanium with BCC–HCP (α − ε) reorganization is associated with initiation of the driving wave process by the elastic field of screw segments of rectangular dislocation loops with Burgers vectors along \( {\left\langle 1\overline{1}0\right\rangle}_{\upalpha} \) directions. Significant deviation of normals of ℓ-waves (responsible for formation of habits) from planes {110}_α creates conditions for inclusion of s-waves (responsible for formation of twinned crystals) in the wave process during α–γ (BCC–HCP) martensitic transformation. This makes it possible to go through the intermediate γ-phase: α–γ–ε.