Composition formulas of binary eutectics

Abstract

The present paper addresses the long-standing composition puzzle of eutectic points by introducing a new structural tool for the description of short-range-order structural unit, the cluster-plus-glue-atom model. In this model, any structure is dissociated into a 1st-neighbor cluster and a few glue atoms between the clusters, expressed by a cluster formula [cluster]gluex. This model is applied here to establish the structural model for eutectic liquids, assuming that a eutectic liquid consist of two subunits issued from the relevant eutectic phases, each being expressed by the cluster formula for ideal metallic glasses, i.e., [cluster](glue atom)1 or 3. A structural unit is then composed of two clusters from the relevant eutectic phases plus 2, 4, or 6 glue atoms. Such a dual cluster formulism is well validated in all boron-containing (except those located by the extreme phase diagram ends) and in some commonly-encountered binary eutectics, within accuracies below 1 at.%. The dual cluster formulas vary extensively and are rarely identical even for eutectics of close compositions. They are generally formed with two distinctly different cluster types, with special cluster matching rules such as cuboctahedron plus capped trigonal prism and rhombidodecahedron plus octahedral antiprism.

Coherent Precipitation and Strengthening in Compositionally Complex Alloys: A Review

“…Actually, the local chemical structural units (chemical short range orders, CSROs) induced by solute elements are crucial to the stability of parent solid solution at high temperatures [ 138 , 139 ], which decides the precipitation of ordered phase during the aging or as-cast state. The recently-proposed cluster-plus-glue-atom model has defined such local chemical structure units in solid solutions [ 120 , 140 , 141 , 142 ], in which the cluster is the nearest-neighbor polyhedron centered by a solute atom having the strong interaction with the base solvent atoms to represent the strongest CSRO, and some other solute atoms (i.e., glue atoms) with weak interactions are certainly required to fill the space between the clusters to balance the atomic-packing density. Thus, a composition formula of [cluster] (glue atom) x ( x being the glue-atom number) can be obtained from the cluster model.…”

Composition formulas of Fe-based transition metals-metalloid bulk metallic glasses derived from dual-cluster model of binary eutectics

“…As already stated in ref. 26 , binary eutectic liquids are characterized, in terms of the cluster-plus-glue-atom model for describing short-range-order local structures, by: Two stable liquid subunits issued from the two eutectic phases , and Each subunit formulated as [ cluster ]( glue atoms ) 1 or 3 of ideal metallic glasses . …”

“…In this paper, the cluster-plus-glue-atom structural model and the relevant composition formulas will be used to understand the composition rule of Fe-(B,P,C)-based transition metal-metalloid multicomponent BMGs. The above-mentioned difficulties will be particularly addressed, by introducing a new approach towards obtaining the appropriate Fe-(B,P,C)binary cluster formulas, which is based on the dual cluster formulism for eutectic liquids 26 . After obtaining the basic Fe-(B,P,C) formulas, compositions of some typical Fe-(B,P,C) based binary, ternary and multi-component BMGs will be explored on the basis of the binary basic formulas.…”

Hidden electronic rule in the “cluster-plus-glue-atom” model

“…The Zr-Cu/Al ICs and Ti-Al/Cu ICs with apparent cluster features have been studied first 27 29 53 , and their crystallographic information are listed in Supplementary Table SII . Based on the central force field model 29 63 64 65 66 , the cluster structure information of these Zr-Cu/Al and Ti-Al/Cu ICs are obtained. The results are collected in Fig.…”