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Park et al. J Mater Inf 2023;3:5 https://dx.doi.org/10.20517/jmi.2022.37 Page 7 of 25

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Figure 3. Time-temperature cycles defined in the DSC with two different heating rates of 10 °C min and 20 °C min .
the surface tension of the droplet, which changed significantly upon the two-phase separation. In the
present study, the contact angle of the liquid Fe-Sn binary alloy was measured in order to detect the binodal
temperature of the alloy.

The apparatus to measure the contact angle is schematically shown in Figure 4. A sample mass of 2 g of the
Fe-Sn alloy was placed on an alumina substrate, and charged into the hot zone of a horizontal resistance-
heating furnace (Lenton, LTF-17, Parsons Lane, UK with MoSi heating elements of Kanthal U-type) under
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an Ar-5% H (g) atmosphere. Ar-5% H (g) was purified by passing silica gel and CaSO column for moisture
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and ascarite for a trace of CO (g). Since oxygen content could affect the contact angle, Ar-5% H (g) was also
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passed through the Mg and Cu turnings at 500 °C. The oxygen partial pressure was measured using a ZrO 2
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oxygen sensor and its pressure range was ~10 -~10 atm. Ar-5% H (g) was supplied into the furnace with
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a flow rate of 0.2 L min to minimize possible vaporization of the elements. The temperature of the
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horizontal furnace was raised to 1,400 °C at 2 °C min rate and held for 30 min. The melt temperature was
checked using a B-type thermocouple calibrated with the standard thermocouple (CHINO Corp., Model
C800-65, Type B, 0.5 mm in diameter, 1,500 mm in length, Tokyo, Japan). The temperature was lowered to
1,100 °C at 30 °C intervals. After holding temperature for 20 min at each temperature, a photograph was
taken with Nikon Camera (Nikon, D3100, Tokyo, Japan) with a Canon lens (Canon, SIGMA APO 70-300
mm F4-5.6 DG, Tokyo, Japan). After obtaining the photographs, the image was converted into a greyscale
image using Image J. The image was digitized and the digitized data were handled using Microsoft Excel to
run an algorithm developed by Lee et al. based on k-Means clustering [53,54] . This algorithm is an objective
[52]
algorithm that can be adopted without being biased by human decisions, and it was shown to be effective in
[52]
extracting the contact angle of a droplet. Details of this algorithm can be found elsewhere .
RESULTS OF EXPERIMENTAL INVESTIGATIONS
Phase equilibria obtained by DSC