PS26
Hetero-3D の ISS-ELF 実験で溶融凝固させた
TiC 添加 Ti-6Al-4V 試料の表面解析
Surface Analysis for Ti-6Al-4V with TiC Melted andSolidified in the ISS-ELF Experiment of Hetero-3D
上野遥か 1, 門井洸衛 1, 上田雄翔 1, 櫛舎祐太 1, 馬渕勇司 1, 花田知優 1, 左口凌成 2, 山田素子 2,佐藤尚 2, 渡辺義見 2, 中野禅 3, 小山千尋 4, 織田裕久 4, 石川毅彦 4, 渡邊勇基 5, 鈴木進補 1
Haruka UENO1, Koei KADOI1, Yuto UEDA1, Yuta KUSHIYA 1, Yuji MABUCHI1, Chihiro HANADA1,Ryosei SAGUCHI2, Motoko YAMADA2, Hisashi SATO2, Yoshimi WATANABE2, Shizuka NAKANO3,Chihiro KOYAMA4, Hirohisa ODA4, Takehiko ISHIKAWA4, Yuki WATANABE5,and Shinsuke SUZUKI1早稲田大学，Waseda University,
名古屋工業大学，Nagoya Institute of Technology (NITech),
3 株式会社 Henry Monitor，Henry Monitor Inc.,
4 宇宙航空研究開発機構，Japan Aerospace Exploration Agency (JAXA),
5 株式会社エイ・イー・エス，Advanced Engineering Services (AES)1
2

1.

Introduction
To clarify the solidification behavior of Ti-6Al-4V with TiC heterogeneous nucleation site particles,

Hetero-3D mission was carried out. The samples were melted and solidified using the electrostatic levitation
furnace in the International Space Station (ISS-ELF) and the electrostatic levitation furnace on the ground (ESL).
After the experiments, streak patterns were observed on the surfaces of the ISS-ELF samples, which were noton those of the ESL samples1). Therefore, the objective of this study was to clarify the surface condition of theISS-ELF sample by comparing the streak patterns observed only on it and the grain map on the cross section.
2.

Experimental Procedures
The mixed powder Ti-6Al-4V with 5 mass% TiC was sintered and cut into cubes of about 25 mg.

Subsequently, the sample was formed into a spherical shape in an arc furnace for stable levitation. The sample
was levitated among electrodes and heated using four laser beams in the ISS-ELF. After melting, the sample
was solidified by natural cooling under the Ar atmosphere2). The recovered sample was embedded in resin,
cut using a diamond wire saw at about 300 µm from the top of the sample, and polished using a polishingmachine. Subsequently, electron backscatter diffraction (EBSD) analysis was conducted to obtain the priorb grain map on the cross section3). In addition, scanning electron microscopy (SEM) was used to observe thestreak patterns on the surface of the sample.
3.

Results and discussion
1 of 2

The SEM image of the entire view of the ISS-ELF sample shown in Fig. 1(a) confirmed streak patterns on
the entire surface of the sample. In addition, the SEM image of the isometric view shown in Fig. 1(b) confirmed
some streak patterns in the edge of the cross section. The SEM image of the cross section and the prior-b grain
map overlapped with the direction fixed so that the dimensions matched were shown in Fig. 1(c). The
observation of multiple crystal grains in the cross section indicates that the crystal grains were refined.
Focusing on the edge of the cross section, it was confirmed that the positions of the prior-b grain boundaries
and the streak patterns approximately matched. Furthermore, an image of the streak pattern observed by highmagnification is shown in Fig. 1(d). This confirmed that the streak patterns observed on the surface of thesample were steps. These results indicate high possibility that the steps observed in the ISS-ELF samples weregenerated at the prior-b grain boundaries.

Figure 1.

Images of the ISS-ELF sample obtained by SEM. The entire image before polishing was shown in (a). The
cross-sectional images after polishing shown in (b)and(c). They have different part of view. To clarify thepositional relationships, the streak patterns were traced in the image shown in (c). In the image shown in (d),dark gray areas are cross sections and gray areas are surfaces, with the boundary traced for clarity. Inaddition, the sample surface was drawn with an auxiliary line to clarify that it was a step.

4.

Conclusions
The streak patterns on the surface of the ISS-ELF sample were steps. In addition, the steps approximately

matched with the positions of the prior-b grain boundaries. This result clarified the high possibility on thesample were generated at the prior-b grain boundaries.
References
1)

2)
3)

C. Hanada, H. Aoki, Y. Mabuchi, Y. Ueda, K. Kadoi, K. Yoneda, R. Saguchi, M. Yamada, H. Sato, Y. Watanabe, Y.
Harada, S. Ozawa, S. Nakano, C. Koyama, H. Oda, T. Ishikawa, Y. Watanabe, T. Shimaoka, and S. Suzuki: Poster ofASGSR (2023).
Y. Kushiya, Y. Mabuchi, C. Hanada, Y. Ueda, K. Kadoi, H. Aoki, R. Saguchi, M. Yamada, H. Sato, Y. Watanabe, C.
Koyama, H. Oda, T. Ishikawa, Y. Watanabe, and S. Suzuki: Abstract of JASMAC-35 (2023) P24.
Y. Mabuchi, H. Aoki, C. Hanada, Y. Ueda, K. Kadoi, Y. Kushiya, R. Saguchi, K. Yoneda, M. Yamada, H. Sato, Y.
Watanabe, S. Ozawa, S. Nakano, C. Koyama, H. Oda, T. Ishikawa, Y. Watanabe, T. Shimaoka, and S. Suzuki: HeatingConditions in Electrostatic Levitation Experiments for Grain Refinement of Ti-6Al-4V with TiC. Int. J. Microgravity
Sci. Appl., 41 (2024) 410201, DOI: 10.15011/jasma.41.410201.
© 2024 by the authors. Submitted for possible open access publication under
the terms and conditions of the Creative Commons Attribution (CC BY) license(http://creativecommons.org/li censes/by/4.0/).
2 of 2