Investigations on metallurgical parameters in hypoeutectic Al-Si alloys under upward directional solidifications

The solidification thermal parameters such as solidification speed, cooling rate, and local solidification time were determined and correlated with tertiary dendritic arm spacings. Microsegregation profiles were experimentally determined from the central region of the dendritic arms to the interdendritic regions under different solidification speeds. A phase-field model was considered in the simulations of the solidification process in hypoeutectic Al-Si alloys. In order to improve the predictive capacity of the present model, the solidification speed effects were considered through the incorporation of the effective partition coefficients. Those partition coefficients, in turn, have been experimentally determined for a wide range of solidification speeds. The values of effective partition coefficient and cooling rate obtained from experiments were considered in the calculations. The tertiary dendrite arm spacings for both alloys were predicted by the phase-field model in regions close to the water-cooled system. The present-work-based numerical results show a good agreement with dendrite arm spacings determined from the experimental procedure. The microsegregation phenomenon, which is the inhomogeneous distribution of solute at the scale of dendrite spacings, was calculated by the phase-field model. The microsegregation profiles of silicon solute, determined by the model, yielded appreciable agreement from the experimental data. Finally, solidification speed was predicted by the model. While effective partition coefficient and cooling rates obtained from experiments were considered during calculations, a good agreement can be observed for solidification speed. Through numerical examples, the applicability of the phase-field model to the problems of dendrite arm spacings, microsegregation, and solidification speed in Al-Si alloys directionally solidified is demonstrated.

Automated summary

This study investigates the thermal parameters, tertiary dendritic arm spacings, microsegregation, etc., in the solidification process through experiments and simulations, and predicts and analyzes using the phase-field model.