Activity Interaction Coefficients of Si in Cu-Ti-Si Melts at 1550℃

Activitibs of Si in binary Cu-Si and ternary Cu-Ti-Si melts were measured at 1 550℃ by using a method of chemical equilIbrium between gas and liquid. The activity interaction coefficients of Si in the melts have been determined from the experimental data (lny = -5.69. s = 6.69. P2: = -26.22. E; =-43.96) and activity interaction coefficients of Ti in binary Cu-Ti melt at 1550℃ has been estimated from Sommer's data based on the regular solution model (lny =-1 .10. : = 2.95.p:=-2.10).

Comparison of Some Methods on Prediction of Activity Interaction Coefficient

Based on Miedema's semiempirical formation enthalpy model for binary alloys, free volume theory and ageneral solution model, a new model for prediction of activity interaction coefficient ε is proposed. The calculatedresults are better in agreement with the experimental values than the two previous models. The related theories andmodels are discussed according to the degree of agreement with experimental values.

Thermodynamics of Fe-P-C in Mn-Based Solutions

The solubilities of carbon in Mn based alloys containing P have been measured at 1 400 ℃ based on X C=0.271 9-0.094 0 X Fe -1.195 4 X P. By means of thermodynamic derivation and calculation, the relative activity coefficients and interactive parameters were derived.

THERMODYNAMICS OF Mn-C-j MELTS AT 1350℃

The solubility of C in Mn melt at different contents of Si at 1350℃ was determined.The sol- ubility of Ca in Mn melts containing C in CaC_2 crucible under sealed condition at 1350℃ was ascertained.With these data,evaluation of the activity interaction coefficients e_C^(Si),e_C^C, e_C^(Ca) as well as γ_C^0 was made.The standard free energy of solution of C in liquid Mn based on the 1 wt-% solution standard,formulated in relation to T,was also estimated.Brief dis- cussion was made as to the confiormability of results with those given in the literature.

Relationship between Thermodynamic Parameters for Mn-Fe Melt and Temperature

The carbon solubility in Mn-Fe melts were measured at 1350℃,1375℃,1425℃and 1450 ℃,and accordingly the calculated equations were obtained.By thermodynamic derivation and calculation,some relationships between thermodynamic parameters for Mn-Fe melt and temperature were obtained.

Thermodynamics of Fe-C-j (j=Al, Si, P, S) Melts

Based on a proposed method, the mathematical expressions between carbon solubility in Fe-C-j (j=Al, Si, P, S) melts and temperature were obtained. The expressions show the relation of the affecting factors of component j and temperature on carbon solubility, and the activity interaction coefficient of j upon carbon depends on atomic number, covalent radius and electro-negativity. The affecting factors of four elements on carbon solubility are all negative. There is a linear relationship between covalent radius and electro-negativity.

Thermodynamic Properties of Mn-C Melts

Carbon solubility in Mn-Fe melts（xMn=0.161-0.706,xFe=0.034-0.633）was measured experimentally at various temperatures.By thermodynamic derivation and calculation,the relationship between activity coefficient of carbon in infinite dilute solution of manganese in Mn-C system and temperature was obtained.Using Gibbs-Duhem relationship,the experimental results of this study,and experimental data reported in references,the relationship between other thermodynamic properties in Mn-C system and temperature were obtained by thermodynamic derivation and calculation.