Effect of sheet thickness on the solidification and quality of Al-Mg2Si composite sheet fabricated by continuous casting

Abstract

Fabrication of particle-reinforced metal matrix composite sheets using twin-roll casting (TRC) encounters quality challenges in the cast product, constraining its industrial viability. The present study investigates the effect of variable sheet thicknesses (3 mm, 4 mm and 5 mm) on the quality of composite sheets fabricated through TRC. The effects of sheet thickness on the thermal-fluid behavior of composite sheets in the TRC process were modeled using the finite element method. The model was validated by comparing the calculated inter-lamellar spacing with those measured through the experiment. As the sheet thickness increases, heat flux along the roll surface increase and colling rate decreases at a constant inlet temperature. Therefore, lowering the inlet temperature with increased sheet thickness helps to increase the cooling rate from the roll surface. Hence, an increased sheet thickness requires a lower inlet temperature to fabricate a composite strip successfully. The optimized inlet temperatures of 836 K, 831 K, and 826 K were suggested for fabricating Al-Mg₂Si composite sheets of 3 mm, 4 mm, and 5 mm thickness, respectively. The thicker sheet experiences a more pronounced variation in velocity vector, suggests that the thinner sheet (3 mm) fabrication is more favorable for continuous casting than a thicker sheet (5 mm). A cooling rate of less than 50 K/s for a 3 mm thickness sheet in TRC process leads to incomplete solidification, posing a risk of sheet breakout during the continuous casting operation. Increasing the sheet thickness from 3 mm to 5 mm increases tendency of porosity formation and centreline shrinkage from 3.8 % to 10.5 %.