Formation of [formula omitted] contraction twins in titanium through reversible martensitic phase transformation

Abstract

We report the discovery of a non-conventional {112¯2} twinning mechanism in α-titanium through reversible α→ω→α martensitic phase transformations. Specifically, the parent α-phase first transforms into an intermediate ω-phase, which then quickly transforms into a twin α-phase, leading to the formation of {112¯2} contraction twins. In addition, we prove that the reversible α→ω→α phase transformations follow strict orientation relations between the parent α-, intermediate ω-, and twin α-phases. Finally, we demonstrate that our mechanism agrees with classical twinning theory in the shuffle, shear, and conjugate twinning plane. This study reveals the important role of the intermediate ω-phase in the twinning process, adding critical details to the existing mechanism of {112¯2} twinning.