CALCULATION OF PHASE-DIAGRAMS AND SOLIDIFICATION PATHS OF AL-RICH AL-LI-CU ALLOYS

Thermodynamic models for the various phases in the Al-rich corner of the Al-Li-Cu system were developed on the basis of the phase equilibrium and limited thermodynamic data available in the literature and the thermodynamic descriptions of the three constituent binary systems, Al-Li, Al-Cu, and Cu-Li. The calculated isothermal sections at several temperatures and the liquidus projection are in agreement with experimental determinations. Combining the thermodynamic models and the Scheil model or the modified Scheil model to include solid-state back-diffusion, quantitative solidification paths were predicted. The calculated amount of the primary phase formed during solidification was compared with those obtained experimentally.