High-pressure torsion of titanium at cryogenic and room temperatures: Grain size effect on allotropic phase transformations

Kaveh Edalati, Takeshi Daio, Makoto Arita, Seungwon Lee, Zenji Horita, Atsushi Togo, Isao Tanaka

研究成果: ジャーナルへの寄稿学術誌査読

66 被引用数 (Scopus)

抄録

Titanium in the form of bulk and powder was processed by severe plastic deformation using high-pressure torsion (HPT) at cryogenic and room temperatures to investigate the influence of grain size on allotropic phase transformations. Almost a complete α (hexagonal close-packed, hcp) to ω (hexagonal) phase transformation occurred under a pressure of 6 GPa at room temperature until the grain size reached the submicrometer level, while the formation of β (body-centered cubic, bcc) phase was not detected. The ω-phase fraction and the ω → α transition temperature decreased with processing at cryogenic temperatures and/or with using powders, i.e. with decreasing the grain size to the nanometer scale during the deformation. First-principles calculations found the β phase to be dynamically unstable (neither stable nor metastable), while both α and ω phases are dynamically stable at 0 and 6 GPa. This explains why the β phase was not detected in this study using different methods such as X-ray diffraction analysis, high-resolution transmission electron microscopy, automated crystal orientation mapping and electrical resistivity measurements. Mechanical properties of the HPT-processed Ti were also examined.

本文言語英語
ページ(範囲)207-213
ページ数7
ジャーナルActa Materialia
68
DOI
出版ステータス出版済み - 4月 15 2014

!!!All Science Journal Classification (ASJC) codes

  • 電子材料、光学材料、および磁性材料
  • セラミックおよび複合材料
  • ポリマーおよびプラスチック
  • 金属および合金

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