Ternary eutectic alloys, Al-CuAl
2-NiCu
3Al
6, Al-CuAl
2-FeCu
2Al
7 and Al-CuAl
2-Si, consisting of Al-CuAl
2 lamellar eutectics and Al-Al
3Ni, Al-Al
3Fe or Al-Si fibrous eutectics, were solidified unidirectionally over a wide range of rates. These microstructures are compared with those of concomitant binary eutectics and are discussed with reference to the term of entropy of fusion of each phases. In Al-CuAl
2-Si ternary eutectics, Si grows with prefered 〈100〉 fiber texture as in Al-Si binary eutectics, though Al-CuAl
2 lamellar are degenerated thoroughly. This is considered to come from the difference of entropy of fusion between Si and CuAl
2, because the entropy of fusion of Si is higher than that of CuAl
2. On the other hand, in Al-CuAl
2-NiCu
3Al
6 ternary eutectics, Al-CuAl
2 lamellae are maintained because the difference in the entropy of fusion between NiCu
3Al
6 and CuAl
2 is smaller than that of Si and CuAl
2. It may be concluded that with increasing entropy of fusion of the third phase, the influence of Al-CuAl
2 on the Al-CuAl
2 lamellae becomes greater.
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