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微小重力下における Fe-60atomic%Cu 合金の相分離挙動
Phase Separation Phenomena of Liquid Fe-60atomic%Cu
Alloys under the microgravity condition
正木匡彦 1, 村田駿１、武川竜弥１,敷地駿１, 小畠秀和２，白鳥英３, 織田裕久４, 小山千尋４，下西里奈４，石川毅彦４, 永山勝久１Tadahiko MASAKI1, Shun MURATA1, Tatsuya TAKEKAWA1, Shun Shikichi1, Hidekazu
KOBATAKE2 ,Shigeru SHIRATORI3, Hirohisa ODA4, Chihiro KOYAMA4, Rina SHIMONISHI4,Takehiko ISHIKAWA4 and Katsuhisa NAGAYAMA1
芝浦工業大学，Shibaura Institute of Technology#1,
同志社大学，Doshisya Univ.#2,
3 東京都市大学，Tokyo City Univ.#3
4
宇宙航空研究開発機構，JAXA#4
121.

Introduction
Fe-Cu alloy is one of the popular peritectic alloys, which has a flat liquidus line around intermediateconcentration range. It is known that when this alloy around intermediate concentration is quenched fromliquid state, a macroscopic liquid phase separation occurs below the liquidus line. Recently, C. P. Wang et al.
found that a curious phase separation in atomized Fe-Cu spherical alloys which was formed co-axial multisphere1). Nagayama also make Fe-Cu powders by using atomization with the use of a short drop tube, thesame shape of spherical sample was observed2). This phase separation attracts interest, however, themechanism cannot be revealed because the measurement of the temperature of small particle is quite difficult.
Recently, We proposed to the observation of the phase separations under microgravity condition due to theelectrostatic levitation furnace, ELF, which is installed on the ISS. Microgravity experiments were performed
successfully and the characteristic cooling curves were obtained. The metallographic structure of retrieved
samples are investigated with the use of electron probe micro analyzer (EPMA). In this report, we show thequick review of the metallographic structure of Fe-60atomic%Cu sample.
2.

Experiments and Results

2.1. Microgravity Experiments
For microgravity experiments with the use of ELF, spherical Fe-Cu alloys whose diameter were around 2mm
were prepared via the gas-jet levitator coupled with laser diodes. Concentrations of samples were Fe 30Cu70,Fe40Cu60, Fe50Cu50, Fe60Cu40, Fe70Cu30 in atomic percent, those were covered the intermediate concentration
range of Fe-Cu alloys. Samples were installed in the sample holder of ELF and launched to the ISS. The sample
was levitated in the chamber of ELF and heated by lasers. Retrieved samples were buried in resin and grind
and polished each 50 micrometers via automatic polisher (Tegra-Pol 25, Struers). Its metalogical structure was
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observed by electron probe micro analyzer (EPMA-8050G, Shimadzu).
2.2. Results and discussion
Figure 1 shows the cooling curve around the solidification temperature under microgravity condition. Aphoto image of camera installed in the pyrometer was superimposed on the figure. We suspect that the firstplateau was the signal of the solidification of Fe rich phase, which can be seen the time from 0.5 sec to 10 sec
in figure 1.

Figure 1. Cooling curve of Fe40Cu60 alloy at solidification.

Figure 2. Result of mapping analysis of EPMA

The second plateau which can be seen the time from 17 sec to 18 sec can be regarded as the signal of thesolidification of Cu rich phase. Exothermic signals at the time around 14 sec might be derived fromsolidification of small droplets or shells in the sample.
Figure 2 shows typical metallographic structure via mapping analysis of EPMA. Blue areas were the Cu richphase whose concentration was 81.2mol%Cu. Many dendrites of Fe rich phase can be seen. Circular form ofgreen areas were the Fe rich phases, those were distributed the center of spherical sample. The concentrationof the largest Fe rich phase was 83.52mol%Fe and concentration of other Fe rich phases were almost same. The
exothermic signals of cooling curve as mentioned above might be indicated the delay of solidification of eachspherical area of Fe rich phase. In addition, thin Fe rich phase whose thickness was around one micrometer
was observed at the surface of the sample. The detail of solidification process will be discussed in mypresentation.
References
1)
2)

C. P. Wang, X. J. Liu, I. Ohnuma, R. Kainuma, K. Ishida, Science 297, 990(2002).
Y. Fujiwara, T.Masaki, Proceedings of JASMAC 33 (2021).

© 2024 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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