Measurements and modeling of the microstructural morphology during equiaxed solidification of Al-Cu alloys

Abstract

The morphology predicted by an equiaxed growth model recently presented elsewhere has been compared with quantitative experimental morphology measurements on a range of Al-Cu alloys. In the experiments, the samples have been solidified with a uniform temperature and quenched from the mushy state at the instant when the eutectic temperature was reached. The copper content and the amount of grain-refiner additions have been varied, resulting in both “clover-leaf” and dendritic equiaxed morphologies. Morphology characterization on both the intragranular and extragranular length scales has been performed on the quenched samples. Average heat-extraction rates, grain densities, and alloy compositions from the experiments have been used as input to the equiaxed grain-growth model, and the resulting morphology predictions have been compared with the morphology measurements. For the morphologies observed in the present study, the equiaxed growth model predicts higher values of the internal solid fraction than observed experimentally. This has been indicated to be due to the failure of commonly made modeling assumptions during the later stages of the solidification.