Investigation of Solidification Behavior and Processing Defects in the Continuous Cast Al-Based Composite Sheet

Owing to high productivity and being highly energy-efficient, continuous casting is among the most widely used processes in manufacturing metallic products like slabs, bools, billet and even sheets. Recently, there has been large attention on manufacturing continuous cast metal matrix composite sheets. However, one of the critical challenges in making these sheets is the formation of porosity in the final product, which significantly affects the product's mechanical properties. In present study, the effect of melt pool height on porosity formation in the continuous casting of composite sheets has been studied using experimental and numerical investigation. Numerical investigation was performed using fluid flow and solidification models to analyze the solidification profile of the melt. The experimental work involved casting of composite sheets under varying melt pool heights (4, 6 and 8 cm) using a vertical continuous casting machine. Microscopic observation was made to analyse the microstructure, distribution of reinforcement particles and shrinkage porosities. Porosity was quantified using the relative density principle. The results showed that increase in the melt pool height led to a significant reduction in porosity formation. The numerical simulations revealed that a broader range of solidification profiles contribute to solidification shrinkage at later stages. Specifically, a melt pool height of 4 cm exhibited a wider range of solid fractions at the roller exit, resulting in a porosity level of approximately 10.9%. For continuous operation at 836 K, however, melt pool heights of 6 cm and 8 cm are preferred over 4 cm, as they lead to reduced porosity levels of 7.7% and 2.7%, respectively.