Numerical simulation of microstructure and microporosity morphology in directional solidification of aluminum-copper alloys: Effect of copper content and withdrawal rate

Microporosity formed in the solidification process of Al alloys is detrimental to the alloy properties. A two-dimensional cellular automaton (CA) model was developed to simulate the microstructure and microporosity formation in Al-Cu alloys, considering variations in Cu content and solidification rate. The results indicate that the Cu content primarily influences the growth of microporosity. To validate the model, directional solidification experiments were conducted on Al-Cu alloys with varing Cu contents and withdrawal rates. The experimental results of dendrites and microporosity characteristics agree well with the predictions from the developed model, thus confirming the validity of the model. The alloy’s liquidus temperature, dendrite morphology, and hydrogen saturation solubility arising from different Cu contents have significant effects on microporosity morphology. The withdrawal rate primarily affects the nucleation of hydrogen microporosity by altering cooling rates and dendritic growth rates, resulting in different microporosity characteristics.