Modeling homogenization behavior of Al-Si-Cu-Mg aluminum alloy

The effect of the as-cast secondary dendrite arm spacing and homogenization temperature on the secondary phase dissolution and solute redistribution during homogenization of cast Al-Si-Cu-Mg aluminum alloy was investigated. Particularly, the concurrent dissolution of θ-Al2Cu and Q-Al5Cu2Mg8Si6 phases was studied for the first time. Two modeling approaches were developed using finite-difference analysis to predict the dissolution kinetics; (i) a stationary interface modeling approach in which the interface is considered to be stationary and (ii) a moving boundary modeling approach in which the particle-matrix interface is moving. The dissolving particle shape was considered to be spherical and the dissolution process to be diffusion controlled. The two model predictions were compared against the experimental data obtained from microstructural characterizations. It was shown that although the stationary interface approach provides reasonable results in predicting the dissolution behavior at higher volume fractions of the secondary phase, the results deviate from the experimental measurements at lower volume fractions. On the other hand, the moving boundary approach was capable of predicting the final dissolution time of the secondary phase. It was also shown that the Q-phase does not dissolve completely as opposed to the θ-phase.