: e— °/s ,IREGULAR” EUTECTIC 
©—°/e LAMELLAR EUTECTIC 
wr 
100 
.. 90 
< 80 
Ele 
. 60 
50 
N : 
9 
„+ 30 
20 
be 
— 
——==— UNDERCOOLING (°C) 
Fig. 4 - Variation of the areas fraction "Irregular" eutectic 
with supercooling 
DISCUSSION 
A. Maximum supercooling 
Supercooling of up to 135°C was achieved which was about 100°C lower 
than supercooling achieved by Kattamis and Flemings (4) who have 
reported a value of about 240°C for supercooling of Ni-Sn eutectic 
alloy surrounded by a glass coating. The results of the present inve- 
stigation, however, represent the suvercooling that was attained for 
electromagnetically levitated samples and in a gas stream. The results 
of supercooling might be explained in two ways: 
1. contaminants in the sample, and 
2. failure to homogenize the samvle. 
The contaminant would also act like an innoculating agent and form 
heterogeneous nucleation sites. The presence of heterogeneous nucle- 
ation would cause the material to solidify before the expected degree 
1 of supercooling, thus reducing the experimental supercooling. 
hin The second question is to homogenize the sample. The arc melter 
does not always produce a truly homogeneous sample. In order to get 
higher supercooling it might be possible using samples made in the 
100 200 
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