The Gibbs free energy of nucleation in liquid alloys is related to the volume entropy of nucleation, ∆Sv (entropy change for the solid/liquid system per unit volume of solid phase nucleated). An expression for the nucleation entropy is derived for the special case of regular solution behaviour for the alloy phases, assuming isothermal, isobaric, constant phase-composition conditions are maintained during nucleation. For binary eutectic alloy systems ∆Sv increases as the distribution coefficient decreases and the solute concentration increases up to the eutectic limit. The role of the nucleation entropy in grain refinement and supercooling behaviour of alloys is discussed.
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