A THERMODYNAMIC DESCRIPTION FOR THE TERNARY AL-MG-CU SYSTEM

A thermodynamic description for the ternary Al-Mg-Cu system was obtain ed based on the descriptions of its three constituent binaries and ter nary phase equilibrium and thermodynamic data available in the literat ure. All binary intermetallic phases are assumed to have negligible te rnary solubility. There are five ternary intermetallic phases; three o f them are taken to be line compounds-and two are assumed to be semist oichiometric phases. In view of the extensive experimental data availa ble in the Al-rich corner, particularly for the Al-rich ternary eutect ic, the objective of this study was to develop a thermodynamic descrip tion that allows us to quantitatively calculate the phase equilibria i n the Al-rich corner. The calculated phase equilibria in-the Mg-rich c orner may not be as good as those in the Al-rich corner, and those in the Cu-rich corner should be topologically correct and serve as a guid e for materials researchers to carry out key experiments in the future to establish the phase equilibria in that portion of the system. Neve rtheless, in:the absence bf additional data, the-calculated phase equi libria in-the Cu-rich corner can be used with caution.