Thermodynamic Basis for Cluster Kinetics:  Prediction of the Fragility of Marginal Metallic Glass-Forming Liquids

Due to the inaccessibility of the supercooled region of marginal metallic glasses (MMGs) within the experimental time window, we study the cluster kinetics above the liquidus temperature, T_l, to acquire information on the fragility of the MMG systems. The thermodynamic basis for the stability of locally ordered structure in the MMG liquids is discussed in terms of the two-order-parameter model. It is found that the Arrhenius activation energy of clusters, Δh, is proportional to the chemical mixing enthalpy of alloys, ΔH^chem. Fragility of the MMG forming liquids can be described by the ratio of the absolute ΔH^chem value to the glass transition temperature, T_g. The manner of vitrification during rapid solidification is an important factor for the discrepancy between the data presented in this paper and the prediction of the two-order-parameter model concerning the relation between Δh and the liquid fragility.