Steps and { 11 2¯ 1 } secondary twinning associated with { 11 2¯ 2 } twin in titanium

Journal Article · 12 November 2018 · Acta Materialia

DOI: https://doi.org/10.1016/j.actamat.2018.11.019 · OSTI ID:2346076

Gong, Mingyu ^[1]; Xu, Shun ^[1]; Xie, Dongyue ^[1]; Wang, Shujuan  ^[2]; Wang, Jian  ^[1]; Schuman, Christophe ^[3]; Lecomte, Jean-Sébastien  ^[3]

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1. Univ. of Nebraska, Lincoln, NE (United States)
2. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
3. Universite de Lorraine, Metz (France)

{$$11\overline{2}2$$} twinning commonly takes place in α-titanium (α-Ti). High-resolution transmission electron microscopies (HRTEM) explored various steps along {$$11\overline{2}2$$} coherent twin boundary. Topological model of {$$11\overline{2}2$$} twin revealed twinning disconnections (TDs) that are represented by (b_i, ih_{{$$11\overline{2}2$$}}) corresponding to a step height ih_{{$$11\overline{2}2$$}} and a shear vector b_i. Atomistic simulations were conducted to study the energies and kinetics of TDs. Combining microscopies and atomistic simulations, we concluded that (b₃, 3h_{{$$11\overline{2}2$$}}) is the elementary TD and (b₁, h_{{$$11\overline{2}2$$}}) is the reassemble TD. Steps observed in HRTEM thus can be treated as a reassembly of (b₃, 3h_{{$$11\overline{2}2$$}}) TDs and (b₁, h_{{$$11\overline{2}2$$}}) TDs. In addition, Electron Backscatter Diffraction (EBSD) maps revealed {$$11\overline{2}2$$} → {$$11\overline{2}1$$} double twins in α-Ti. Using two-dimensional and three-dimensional atomistic simulations, we demonstrated the nucleation of (b₁, h_{{$$11\overline{2}2$$}}) TD and {$$11\overline{2}2$$} → {$$11\overline{2}1$$} double twin through the interaction between basal $$\langle$$$$a$$$$\rangle$$ dislocation and {$$11\overline{2}2$$} twin. In conclusion, our results enrich the understanding of {$$11\overline{2}2$$} twinning including TDs, steps, and {$$11\overline{2}1$$} secondary twins in hexagonal metals.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 2346076
• Report Number(s): LA-UR-19-29305
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Vol. 164; ISSN 1359-6454
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English