The Characterization of Eutectic Structures

Many attempts have been made in the past to bring order to the near-bewildering array of eutectic morphologies. These have met with limited success due mainly to the fact that the morphology of a particular eutectic may be highly dependent on both chemical composition and the rate of freezing. This paper shows for binary alloys, at least, that a more complete understanding of eutectic growth may be obtained by applying a few simple ‘rules’. With these it is possible to so characterize eutectic growth that the unknown structure of a particular eutectic may be prodicted at a given growth rate if the entropy of solution and re­lative volume of each phase are known. The characterization scheme embraces the growth behaviour of the thirty or so systems for which thermodynamic data are more readily available.