TY - JOUR
T1 - Quantifying the dislocation structures of additively manufactured Ti–6Al–4V alloys using X-ray diffraction line profile analysis
AU - Yamanaka, Kenta
AU - Kuroda, Asumi
AU - Ito, Miyu
AU - Mori, Manami
AU - Bian, Huakang
AU - Shobu, Takahisa
AU - Sato, Shigeo
AU - Chiba, Akihiko
N1 - Funding Information:
This research was supported by the Grant-in-Aid for Young Scientists (A) from the Japan Society for the Promotion of Science (JSPS) (Grant No. 17H04957); the Grant-in-Aid for Scientific Research in a Priority Area on “Creation of Life Innovation Materials for Interdisciplinary and International Researcher Development” from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan; the Japan Titanium Society; the Iketani Science and Technology Foundation, Japan (Grant No. 0291050-A); and the Light Metal Educational Foundation, Inc, Japan.The authors would like to thank Yoshihiko Nagata and Kenya Kurita (Koiwai Co. Ltd.) for sample preparation and Issei Narita, Yumiko Kodama, Shun Ito, and Yuichiro Hayasaka (Institute for Materials Research, Tohoku University) for SEM observations, FIB sampling, and TEM observations. Kazuo Yoshida and Haruka Shima (Institute for Materials Research, Tohoku University) are also acknowledged for their technical assistance. This work was performed under the Shared Use Program of JAEA Facilities (Proposal No. 2017A-E13) with the approval of Nanotechnology Platform project supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The synchrotron radiation experiments were performed at the BL22XU of SPring-8 with the approval of the Japan Atomic Energy Agency (JAEA) (Proposal No. 2017A3740).
Funding Information:
The authors would like to thank Yoshihiko Nagata and Kenya Kurita (Koiwai Co., Ltd.) for sample preparation and Issei Narita, Yumiko Kodama, Shun Ito, and Yuichiro Hayasaka (Institute for Materials Research, Tohoku University) for SEM observations, FIB sampling, and TEM observations. Kazuo Yoshida and Haruka Shima (Institute for Materials Research, Tohoku University) are also acknowledged for their technical assistance. This work was performed under the Shared Use Program of JAEA Facilities (Proposal No. 2017A-E13 ) with the approval of Nanotechnology Platform project supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The synchrotron radiation experiments were performed at the BL22XU of SPring-8 with the approval of the Japan Atomic Energy Agency (JAEA) (Proposal No. 2017A3740 ).
Funding Information:
This research was supported by the Grant-in-Aid for Young Scientists (A) from the Japan Society for the Promotion of Science (JSPS) (Grant No. 17H04957 ); the Grant-in-Aid for Scientific Research in a Priority Area on “Creation of Life Innovation Materials for Interdisciplinary and International Researcher Development” from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan; the Japan Titanium Society; the Iketani Science and Technology Foundation , Japan (Grant No. 0291050-A ); and the Light Metal Educational Foundation, Inc, Japan.
Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2021/1
Y1 - 2021/1
N2 - Ti–6Al–4V alloy is widely used in aerospace and biomedical industries, and its preparation using additive manufacturing techniques has recently attracted considerable attention. Herein, the dislocation structures developed during electron beam and laser beam powder-bed fusion (EB-PBF and LB-PBF, respectively) of the Ti–6Al–4V alloy were quantitatively examined via X-ray diffraction (XRD) line profile analysis. The microstructures of both as-built samples were characterized, revealing fine acicular microstructures attributable to a β → α' martensitic transformation. While a fully α'-martensite matrix with a high dislocation density was formed and preserved during the LB-PBF process, the decomposition of the α'-martensite toward the thermodynamically stable α + β microstructure occurred during EB-PBF as a result of post-solidification exposure to high temperatures. Accordingly, a higher dislocation density and finer crystallite size were observed at the top cross-section from the XRD line profile analysis, suggesting that the extent of phase decomposition depended on the duration of the exposure to the elevated temperature. Nonetheless, the saturated dislocation density was as high as 1014 m−2, where dislocation strengthening affected the overall strength of the EB-PBF specimen. Diffraction peaks of sufficient intensity that enabled the analysis of the dislocation structures in both the α (α')-matrix and the nanosized β-phase precipitates at the α (α')-laths were obtained under high-energy synchrotron radiation; this revealed that the β-phase had a much higher dislocation density than the surrounding α (α')-matrix. The enhanced dislocation accumulation in the nanosized β-phase precipitates probably reflects the elemental partitioning that occurred during post-solidification cooling. The valuable insights provided in this study are expected to promote further development of alloy preparation using additive manufacturing processes.
AB - Ti–6Al–4V alloy is widely used in aerospace and biomedical industries, and its preparation using additive manufacturing techniques has recently attracted considerable attention. Herein, the dislocation structures developed during electron beam and laser beam powder-bed fusion (EB-PBF and LB-PBF, respectively) of the Ti–6Al–4V alloy were quantitatively examined via X-ray diffraction (XRD) line profile analysis. The microstructures of both as-built samples were characterized, revealing fine acicular microstructures attributable to a β → α' martensitic transformation. While a fully α'-martensite matrix with a high dislocation density was formed and preserved during the LB-PBF process, the decomposition of the α'-martensite toward the thermodynamically stable α + β microstructure occurred during EB-PBF as a result of post-solidification exposure to high temperatures. Accordingly, a higher dislocation density and finer crystallite size were observed at the top cross-section from the XRD line profile analysis, suggesting that the extent of phase decomposition depended on the duration of the exposure to the elevated temperature. Nonetheless, the saturated dislocation density was as high as 1014 m−2, where dislocation strengthening affected the overall strength of the EB-PBF specimen. Diffraction peaks of sufficient intensity that enabled the analysis of the dislocation structures in both the α (α')-matrix and the nanosized β-phase precipitates at the α (α')-laths were obtained under high-energy synchrotron radiation; this revealed that the β-phase had a much higher dislocation density than the surrounding α (α')-matrix. The enhanced dislocation accumulation in the nanosized β-phase precipitates probably reflects the elemental partitioning that occurred during post-solidification cooling. The valuable insights provided in this study are expected to promote further development of alloy preparation using additive manufacturing processes.
KW - Dislocation structure
KW - Martensitic transformation
KW - Powder bed fusion
KW - Ti–6Al–4V alloy
KW - X-ray diffraction line profile analysis
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U2 - 10.1016/j.addma.2020.101678
DO - 10.1016/j.addma.2020.101678
M3 - Article
AN - SCOPUS:85095612478
VL - 37
JO - Additive Manufacturing
JF - Additive Manufacturing
SN - 2214-8604
M1 - 101678
ER -