Thermodynamic description of the Al–Cu–Mg–Mn–Si quinary system and its application to solidification simulation

By means of the first-principles calculations, the enthalpy of formation for the quaternary phase in the Al–Cu–Mg–Si system was computed. A set of self-consistent thermodynamic parameters for the Al–Cu–Mg–Si and Al–Cu–Mn–Si systems was then obtained using CALPHAD approach taking into account the reliable experimental data and the first-principles calculations. The thermodynamic database for the Al–Cu–Mg–Mn–Si system was developed based on the constituent binary, ternary, and quaternary systems. Comprehensive comparisons between the calculated and measured phase diagrams and invariant reactions showed that the experimental information was satisfactorily accounted for by the present thermodynamic description. The obtained database was used to describe the solidification behavior of Al alloys B319.1 (90.2Al–6Si–3.5Cu–0.3Mg, in wt.%) and B319.1 + xMn (x = 0.5–2, in wt.%) under Gulliver–Scheil non-equilibrium condition. The reliability of the present thermodynamic database was also verified by the good agreement between calculation and experiment for Gulliver–Scheil non-equilibrium solidification.