P25
Ti6Al4VGrain Refinement Simulation of Ti6Al4V
in Electrostatic Levitation Experiments
1,1,1,1,1,2,2,,2
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1,,,Yuto UEDA1, Hirokazu AOKI1, Yuji MABUCHI1, Chihiro HANADA1, Koei KADOI1, Yuta KUSHIYA1,Kanae YONEDA2, Ryosei SAGUCHI2, Motoko YAMADA2, Hisashi SATO2, Yoshimi WATANABE2,and Shinsuke SUZUKI1
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Waseda University,Nagoya Institute of Technology

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1. Introduction
To clarify the grain refinement mechanism of Ti6Al4V alloy with heterogeneous nucleation site particles
TiC, a space mission named Hetero-3D was conducted using the electrostatic levitation furnace in theInternational Space Station. However, TiC particles added in Ti6Al4V dissolved in a previous study of melting
experiments in the electrostatic levitation (ESL) furnace1). It is unclear how much TiC remains compared to theamount of TiC addition. The objective of this study was to clarify the nucleus setting condition (seed density2))
in the phase-field simulation so as to simulate the numbers of grains formed in the ESL experiments.
2. Experimental Procedures
The spherical samples of Ti6Al4V with 5 mass% TiC1) were melted and solidified by lasers in the ESL furnace,
and the temperature histories were obtained. After the experiments, each sample was polished and the numberof prior-β grains in the region of 750 × 750 μm2 at the center of the cross-section was obtained by using SEMEBSD. In addition, the integral value of heating1) was calculated from the temperature history in each sample.
The integral value was maintained between 5.5 × 107 and 7.5 × 107 K2s in the ESL experiment.
On the other hand, grain refinement simulations were performed by phase-field software MICRESS3) using
the seed density model based on the particle size distribution and mass fraction of the as-received TiC. The
cooling rate was set to 71 K/s according to the calculation result of heat transfer, and the simulation region was
the same as the SEM-EBSD analysis. The physical properties were referenced from a previous study4).
3. Results
The number of prior-β grains obtained by the ESL experiments and simulations are shown in Fig. 1. The
number of prior-β grains in the two ESL samples were 5 and 9, which are consistent with the simulation results
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when seed density conditions correspond to 0.65 - 1.5 mass%.

Figure 1. The number of prior-β grains obtained by ESL experiments and simulations.
4. Discussion
The relationship between the amount of nucleus and the number of grains was approximated in a curve(Fig. 1). In a simulation, nucleus grains are generated from within the target region, while the results of SEMEBSD analyses of ESL samples include grains nucleated outside the target region. Therefore, even though thenumber of prior-β grains in the region is the same as simulation, the actual number of nucleus may be smaller
than that in the simulation. This is inferred from the presence of small grains in the ESL experimental results(Fig. 1).
5. Conclusions
The numbers of grains obtained from the simulations were compared with the numbers of prior-β grainsobtained from the ESL experimental results. As the results, the same numbers of prior-β grains are formed inboth ESL experiments and simulations when seed density corresponds to 0.65 - 1.5 mass%.
Acknowledgements
ESL experiments were conducted with the help of Japan Aerospace Exploration Agency (JAXA) andAdvanced Engineering Services (AES).
References
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Y. Mabuchi, C. Hanada, Y. Ueda, K. Kadoi, Y. Kushiya, H. Aoki, K. Yoneda, R. Saguchi, M. Yamada, H. Sato, Y. Watanabe,
S. Ozawa, S. Nakano, C. Koyama, H. Oda, T. Ishikawa, Y. Watanabe, and S. Suzuki: Abstract of JASMAC-35 (2023).
B. Böttger, J. Eiken, and M. Apel: Phase-field simulation of microstructure formation in technical castings - a self-consistenthomoenthalpic approach to the micro-macro problem. J. Comput. Phys., 228 (18) (2009) 6784, DOI: 10.1016/j.jcp.2009.06.028.
MICRESS, ACCESS Materials and Processes, Aachen, Germany. web.micress.de
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refinement capacity of TiC in directionally solidified Ti6Al4V alloy, Metall. Mater. Trans. A, 52 (2021) 3609,DOI:10.1007/s11661-021-06333-2.
© 2023 by the authors. Submitted for possible open access publication under theterms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/li
censes/by/4.0/).
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