Thermodynamic Research on Solution Properties of Al-Er Alloys

Abstract

Mixing enthalpy of Al-Er binary alloys system has been calculated based on Miedema model, in which a new interaction parameters Li proposed by George Kaptay was considered: Li=h0i.exp(－T/τ0i ), which are used to indirectly calculate the activity of Er in Al-Er alloys and some other thermodynamic properties, such as excess Gibbs energy and excess entropy at 1073K. Firstly the interaction parameter between Al and Er is worked out, then formation ability of alloy solution is analyzed. The results showed that interaction parameter vs temperature can be taken as the form of LAl-Er=－240.29 exp(－T/2000) kJ/mol, which indicates that Al and Er atoms have a great tendency to form intermetallic compound of Al3Er during solidification. The Er concentration shows a negative deviation from Rault’s law, mixing enthalpy, excess Gibbs energy and excess entropy are all negative in the whole range of concentration, which reveals that Al and Er could dissolve each other up the liquidus line.