The classification of binary eutectics

Values of the interface roughness parameter (α) have been calculated for the primary phases of the 12 simple binary eutectic systems for which sufficient thermodynamic data are available; namely, Ag?Bi, Ag?Cu, Ag?Pb, Al?Ge, Al?Sn, Bi?Cd, Bi?Sn, Cd?Pb, Cd?Zn, In?Zn, Pb?Sb and Sn?Zn. It is shown that in the presence of solute the values of α can be significantly different from those of the pure component elements. The calculated, values of α are correlated with eutectic morphologies on the basis of the Hunt and Jackson classification. If the broken lamellar structure is also in the faceted/nonfaceted group then the results are in agreement with Hunt and Jackson’s classification. The analysis is discussed in the light of recent interpretations of the theories of solid-liquid interfaces and resultant growth morphologies. It is concluded that thermodynamic calculations are useful in the prediction of eutectic structures even though they may not necessarily resolve arguments concerning the mechanisms of eutectic solidification.