Abstract
The extension of the thermodynamic solution model of Tanaka et al. to solid binary systems enables us to calculate activity coefficients of solute elements in liquid and in solid phase in infinite dilution. The determination of both activity coefficients in liquid and in solid phase makes it possible to predict the equilibrium segregation coefficient of solute elements in transition metal base alloys without knowledge of binary phase diagrams. The model was applied to Cr, Mo and W base dilute alloys at the melting point of the base metal. The calculated values of equilibrium segregation coefficients are compared with their values determined by using of binary phase diagrams. The effect of input model parameters on the value of equilibrium segregation coefficients is discussed.

Key words
thermodynamic solution model of Tanaka, solid binary systems, Cr, Mo, W base dilute alloys, equilibrium segregation coefficient, binary phase diagrams

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