Thermodynamic Evaluations of the Al-Li-Cu-Mg-Zr Systems

Abstract

The investigation of the Al­Li­Cu­Mg­Zr system is accomplished in this report. The evaluations of the Cu­Mg­Zr and Cu­Li­Mg systems and the experimental study of the Al­Li­Cu­Mg system were carried out during the COST 507 second round. The evaluation of the Cu­Li­Mg system was based on the DSC experiments at the large range of composition. The parameters of the excess Gibbs energy obtained agreed quite well with the temperatures of the phase transformations but the fit was not so good using the experimental enthalpies. The decomposition temperature of the phase was fixed at 702.7 and was not defined earlier in the literature. The optimisation of the Cu­Mg­Zr system was based on the experimental data from the literature and on one set of the DTA experiments measured. The calculated phase diagram was in good agreement with the data used. The existence of the new phase as well as the parameters of formation of the excess Gibbs energy contributed well the system studied. The phase relations near to Al­rich corner containing up to 7 wt.% Li, 7 wt.% Mg and 10 wt.% Cu were investigated using microscopy analysis, quality local X­ray spectral analysis and X­ray phase analysis in the experimental study of the Al­Li­Cu­Mg system done by Baikov Institute of Metallurgy.