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Title: Multimodal assessment of mechanically induced transformation in metastable multi‐phase steel using X‐ray nano‐tomography and pencil‐beam diffraction tomography
Authors: Toda, Hiroyuki
Hirayama, Kyosuke  kyouindb  KAKEN_id  orcid https://orcid.org/0000-0001-5312-5032 (unconfirmed)
Okamura, Kai
Suzuki, Takafumi
Takeuchi, Akihisa
Uesugi, Masayuki
Fujihara, Hiro
Author's alias: 戸田, 裕之
平山, 恭介
岡村, 海
鈴木, 尚史
竹内, 晃久
上椙, 真之
藤原, 比呂
Keywords: Mechanically induced transformation
C-Mn-Si steel
Nano-tomography
X-ray diffraction
Mechanical driving force
Issue Date: 1-Aug-2022
Publisher: Elsevier BV
Acta Materialia Inc.
Journal title: Acta Materialia
Volume: 234
Thesis number: 117956
Abstract: A combination of X-ray nano-tomography and pencil-beam diffraction tomography was utilized for multimodal assessment of the mechanically induced transformation of individual retained austenite grains during tensile deformation in a 0.1C-5Mn-1Si multi-phase steel. In the present study, a newly developed high energy (20 - 30 keV) and high resolution (spatial resolution of 0.16 µm in this study) X-ray nano-tomography technique was applied for the first time to the in-situ observation of a steel under external loading. The gradual transformation, plastic deformation, and rotation behaviour of the individual austenite grains were clearly observed in 3D. It was revealed that the early stage of the transformation was dominated by the stress-assisted transformation that can be associated with measured mechanical driving force, whilst the overall transformation was dominated by the strain-induced transformation that is interrelated with measured dislocation multiplication. The transformation behaviour of individual grains was classified according to their initial crystallographic orientation and size. Noteworthy was the high stability of coarse austenite grains (i.e., 2.5 μm or larger in diameter), contrary to past reports in the literature. Characteristic rotation behaviour and wide data dispersion were also observed in the case of the individual austenite grains. It was conclusively demonstrated that such characteristic behaviour partly originated from interactions with surrounding soft and hard phases. The origins of these characteristics are discussed by combining the image-based and diffraction-based information.
Description: 【研究成果】次世代自動車用鋼板の外力による内部組織の変化を直接観察 --複合X線CT解析技術の開発--. 京都大学プレスリリース. 2022-05-16.
Rights: ©2022 The Authors. Published by Elsevier Ltd on behalf of Acta Materialia Inc.
This is an open access article under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International license.
URI: http://hdl.handle.net/2433/274311
DOI(Published Version): 10.1016/j.actamat.2022.117956
Related Link: https://www.t.kyoto-u.ac.jp/ja/news/topics/research/20220516_2
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