Formation of {11(2)over-bar2} contraction twins in titanium through reversible martensitic phase transformation

We report the discovery of a non-conventional {11 (2) over bar2} twinning mechanism in alpha-titanium through reversible alpha -> omega -> alpha martensitic phase transformations. Specifically, the parent alpha-phase first transforms into an intermediate alpha-phase, which then quickly transforms into a twin omega-phase, leading to the formation of {11 (2) over bar2} contraction twins. In addition, we prove that the reversible alpha -> omega -> alpha phase transformations follow strict orientation relations between the parent alpha-, intermediate omega-, and twin alpha-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 omega-phase in the twinning process, adding critical details to the existing mechanism of {11 (2) over bar2} twinning. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study reports the discovery of a non-conventional twinning mechanism in alpha-titanium through reversible alpha -> omega -> alpha martensitic phase transformations. It demonstrates the important role of the intermediate omega-phase in the twinning process, adding critical details to the existing mechanism of {11 (2) over bar2} twinning. The study also confirms strict orientation relations between the parent alpha-, intermediate omega-, and twin alpha-phases.