The role of {101¯2} tension and {112¯2} compression twins on the α to ω phase transformation in Ti

Abstract

The role of preexisting twin networks on the phase transformation from hexagonal close packed (HCP) $\alpha$ Ti to $\omega$ hexagonal Ti remains relatively unexplored. In this work, we study these effects from both thermodynamics and kinetics standpoints. We utilize an isotropic and linear elasticity micromechanical model alongside MD simulations to determine the effects of preexisting twins on the stability of $\omega$ nucleus. It is found that from a thermodynamic standpoint, both preexisting $\left\{10\overline{1}2\right\}$ tension and $\left\{11\overline{2}2\right\}$ compression twins promote nucleation of $\omega$ nucleus (with non-cozone orientation relationship) within the twin, with the former having a greater effect in reducing the critical radius and thus the overall activation barrier. MD simulations reveal that the growth of the $\omega$ nucleus is stopped by the $\left\{11\overline{2}2\right\}$ CTB but not the $\left\{10\overline{1}2\right\}$ CTB; thereby showing the role of short-range pinning of boundaries.