Al-cu-x (x = Cd, In) Thermodynamic Optimization And Calculation

Aluminum alloys are widely used due to their light weight, high strength, good electrical and thermal conductivity, high plasticity, harmless to the environment, as well as the abundance of the mineral resources. Nowadays, development of Al-Cu based alloys with high strength and high ductility is a hot issue in this area. Researchers find that adding trace elements such as Cd, In, etc. in the Al-Cu alloy can increase the nucleation rate ofθ' phase, which can remarkably refine theθ' phase and improve the strengthen of Al alloy. Phase diagram is the map to the material research. To understand this phenomenon, accurate phase diagram and thermodynamic parameters is indispensable.. In this work, based on the experimental phase diagram and thermodynamic data, the CALPHAD technique was applied to optimize Al-Cd, Cu-Cd and Al-In three binary systems . Togather with the thermodynamic parameters of Al-Cu and Cu-In binary systems from literatures, Al-Cu-Cd and Al-Cu-In ternary systems were extrapolated reasonably and a thermodynamic database of these 2 ternary systems were established. The main works of this thesis are:1. Experimental data on phase diagram and thermodynamic properties were reviewed for three ternary systems Al-Cd, Cu-Cd and Al-In. By CALPHAD approach, the Al-Cd system was re-optimized adopting the up-to-date and widely-accepted lattice stability parameters, while Cu-Cd and Al-In systems were optimized for the first time. Substitutional solution model was applied for liquid and solution phases. All the other intermetallic compounds were treated as stoichiometric ones other than Cd₈Cu₅, which was treated using two-sublattice model. The calculated phase equilibria and thermodynamic properties agreed well with experimental data.2. The Al-Cu-Cd ternary system was extrapolated and Al-Cu-In system was optimized associating with obtained thermodynamic parameters of Al-Cd, Cu-Cd and Al-In systems as well as the reported ones of Al-Cu and Cu-In systems. Partial isothermal sections, liquidus projections and isoplethic sections of the two ternary systems were calculated. Good agreement between the calculated results and experimental data has been reached.