Analytical Model for Liquid/Liquid Interfacial Energy of Microalloyed Monotectic Alloys

An analytical model is proposed for the calculation of the interfacial energy γ_L1/L2 between an A-rich matrix liquid and B-rich droplets in an A-B monotectic alloy microalloyed by element I, based on the Gibbs absorption isotherm. The model is applicable to the microalloying element segregated to the liquid/liquid interface or impoverished in the interface. Solidification experimental results validated the model. Calculation results demonstrate that the variation of γ_L1/L2 with I concentration x_I is not always monotonic. It is determined by the dependence of I chemical potential μ_I on x_I, which is closely related to the interaction parameter L_AI in the A-rich corner of the liquid A-I alloy. μ_I increases with x_I monotonically when L_AI < 2R_gT_b,A-B (T_b,A-B is the binodal line temperature), and it shows a tendency with x_I of first increase and then decrease, followed by an increase when L_AI ≥ 2R_gT_b,A-B. The variation trends of γ_L1/L2 and μ_I with x_I are opposite for an element I segregated to the liquid/liquid interface and similar for an element I impoverished in the liquid/liquid interface.