Excess volume and heat of mixing in Cu-Ti liquid mixture

Kurzfassung

The macroscopic quantity describing the chemical ordering in dense liquid binary mixture is the excess volume. However the connection between excess volume, packing and mixing behavior in metallic melts is not yet fully understood. A precise measurement of the density of metallic melts allows a deep insight into the mixing mechanisms and chemical ordering of such systems. The density of the Cu-Ti binary mixture have been measured over the whole composition range by the containerless technique of electromagnetic levitation (EML) as function of the temperature. A linear temperature dependence of the density has been found for all alloys investigated. Therefore the density decreases with the increasing of the Ti content in the alloys showing a negative deviation from the regular solution model. Nevertheless a positive excess volume arises for the deviation of the density from the regular solution.The excess volume behavior has been discussed taking into account the negative enthalpy of mixing the Cu-Ti system and explained in terms of chemical ordering and in particular by a subtle interplay between short range and long range interactions.