Formation of {112¯2} contraction twins in titanium through reversible martensitic phase transformation

Unravelling the nucleation and growth of {11-2¯2} twins

“…The boundaries lie along K1 or K2 planes of the {112 � 2} twin observed experimentally in Ti. It was also demonstrated by Zahiri et al [32] that twin nucleated by this mechanism in atomistic simulations has the same K1, K2 and shear value as the experimentally observed twin. It is worth to note that the occurrence of conjugate twin facets was also experimentally observed for other twin types [37].…”

“…The structure was relaxed in LAMMPS [36] by using of conjugate gradient energy minimization after each compression step. Despite the fact that we used much smaller simulation block and performed, in fact, molecular static simulations at 0K instead of molecular dynamics simulations performed in [32], the observed results were similar. We start from α-phase and observed subsequent phase transformation from hcp α-phase to ω-phase and back to another variant of α-phase (see Fig.…”

“…Recently, Zahiri et al [32] demonstrated, applying the MEAM potential developed by Hennig et al [33] that the {112 � 2} twin could occur mediated by a reverse phase transformation. The shear value of the twin obtained in their simulations is equal to the experimentally observed 𝑏𝑏 3/3 mode.…”

“…In this paper, using Hennig MEAM potential [33], we show that a pair of disconnections (𝑏𝑏 𝑡𝑡 and 𝑏𝑏 𝑡𝑡 * ) can be considered as a very wide and dissociated core of 𝑏𝑏 3/3 disconnection, which contains omegaphase structure inside. In order to study the growth of the {112 � 2} twin in detail, we performed atomistic simulations to reproduce the nucleation mechanism presented in [32]. Our simulation block contains hcp structure and has size 41.04 nm in 〈112 � 0〉 direction (x), 1.52 nm in 〈11 � 00〉 direction (y) and 27.9 nm in [0001] direction (z).…”