Lamellar Spacings Determined by Solid-Liquid Interfacial Morphology of Unidirectionally Solidified Al-Base Binary Eutectic Alloys

Abstract

Eutectic phases of binary alloys can often be morphologically lamellar. Referring to λ and V as an interlamellar spacing and solidification rate, respectively, the Jackson-Hunt’s relationship where λ²V is constant⁽¹⁾ has been obtained on minimizing the supercooling during solidification. Prigogzine⁽²⁾ has proposed that the morphology is determined so as to minimize the entropy production in irreversible thermodynamics. This investigation has been undertaken to find the ranges of λ as resultant lamellae in several Al-base eutectic alloys and the results are interpreted in terms of the perturbation theory originally developed by Mullins and Sekerka⁽³⁾. It is found that the interlamellar spacing is determined either by the criterion of minimum supercooling or minimum entropy production depending upon the latent heat of fusion of the eutectics.