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

The morphology predicted by an equiaxed growth model recently presented els ewhere has been compared with quantitative experimental morphology measurem ents on a range of Al-Cir 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 bo th "clover-leaf" and dendritic equiaxed morphologies. Morphology characteri zation on both the intragranular and extragranular length scales has been p erformed on the quenched samples. Average heat-extraction rates, grain dens ities, and alloy compositions from the experiments have been used as input to the equiaxed grain-growth model, and the resulting morphology prediction s have been compared with the morphology measurements. For the morphologies observed in the present study, the equiaxed growth model predicts higher v alues of the internal solid fraction than observed experimentally. This has been indicated to be due to the failure of commonly made modeling assumpti ons during the later stages of the solidification.