Surface Tension of Molten Ag-Sn and Au-Cu Alloys at Different Oxygen Partial Pressures

A semi- empirical method to estimate the surface tension of molten alloys at different oxygen partial pressures is suggested in this study. The surface tension of molten Ag-Sn and Ag-Cu alloys were calculated using the Butler equation with the surface tension value of pure substance at a given oxygen partial pressure. The oxygen partial pressure ranges were 2.86 x 10 (-12) - 1.24 x 10 (-9) Pa for the Ag-Sn system and 2.27 x 10 (-11) - 5.68 x 10(-4) Pa for the Ag-Cu system. In this calculation, the interactions of the adsorbed oxygen with other metallic constituents were ignored. The calculated results of the Ag-Sn alloys were in reasonable accordance with the experimental data within a difference of 8%. For the Ag-Cu alloy system at a higher oxygen partial pressure, the surface tension initially decreased but showed a minimum at X-Ag = 0.05 to increase as the silver content increased. This behavior appears to be related to the oxygen adsorption and the corresponding surface segregation of the constituent with a lower surface tension. Nevertheless, the calculated results of the Ag-Cu alloys with the present model were in good agreement with the experimental data within a difference of 10%.