OXYTHERM project: influence of oxygen on surface tension of liquid Cu-Sn binary alloys

One reason for the success of containerless measurement of thermophysical properties at high temperature is that pollution of the sample material from contact with container walls is avoided. However, even in containerless processing, contact of the liquid with residual gasses acting as surfactant cannot be avoided. Among which, oxygen could be considered the most important one for liquid metals and alloys and its tensio-activity is largely known. This fact is particularly disturbing in the surface tension determination as it introduces an uncontrolled uncertainty into its measurement. It has been argued that surface tension data of liquid metals can only be interpreted when the oxygen partial pressure under which the measurement was carried out is known. Apart from having an effect on the surface, oxygen in contact with a liquid alloy might also affect the bulk thermophysical properties, density and viscosity. The precise knowledge and understanding of this interaction is extremely important for applications, such as welding, soldering, joining, and brazing. Despite this importance, information in literature on this topic is sparse. Cu-Sn and Ag-Cu as binary model systems are planned to be investigated. These systems were chosen, as they are comparatively simple alloy systems with a relative large solubility of oxygen. They can therefore be used as model systems in order to assess and improve available thermodynamic theories for binary alloys