Dual-Cluster Model Of Ti-Cu Binary Eutectic And Composition Interpretation Of Relevant Amorphous Alloys

Glass formation is usually related to deep eutectic points. The present work addresses the composition interpretation of eutectic Ti57Cu43 and relevant bulk metallic glasses (BMGs) by introducing the "dual-cluster" model. In this model, the eutectic liquid structure is presumably composed of two chemical units derived from relevant eutectic phases, each corresponding to a stable liquid satisfying a general cluster formula for ideal metallic glasses [cluster](glue atom)(1or3) in terms of the cluster-plus-glue-atom model. Detailed procedures are introduced to apply this model in interpreting the eutectics, based on which eutectic Ti57Cu43 is interpreted as dual-cluster formulas of 2{[Ti-Cu6Ti8]Cu-3} + [Ti-Cu5Ti9]Ti-3 and 2{[Ti-Cu6Ti8]Cu2Ti} + [Ti-Cu5Ti9]Cu2Ti, where the two clusters [Ti-Cu6Ti8] and [Ti-Cu5Ti9] are, respectively, derived from eutectic phases TiCu and Ti2Cu. Two interpretations are equivalent, and one of the involved chemical units [Ti-Cu6Ti8]Cu-3 = Ti50Cu50 is a basic unit for multicomponent Ti-Cu-based BMGs; typical BMGs are formed by replacing the atoms in the basic unit with alloying ones.