Optimizing the Pouring Temperature for Semisolid Casting of a Hypereutectic Al–Si Alloy Using the Cooling Slope Plate Method

Abstract

This work investigates the optimum pouring temperature during semisolid casting (rheo-casting) of Al–17%Si alloy (A390) to obtain the best combination of microstructure modification and wear resistance. Pouring semisolid slurry was done in both metallic and sand molds to observe the effect of cooling rate on the optimum pouring temperature. The molten metal/slurry was poured into the specified mold type through a cooling slope plate which was continuously water cooled. Different pouring temperatures: 670, 690, 710 and 730 °C, were applied, and their influence on the microstructure and alloy properties was analyzed. Based on the obtained results, the optimum pouring temperature for semisolid casting was decided for the two mold types. Conventional casting was conducted at the optimum temperature in both metallic and sand molds for comparison. It was observed that rheo-casting using the cooling plate is an effective process in microstructure modification of A390 alloy in terms of refining and redistributing the primary Si and fragmenting the coarse AlFeMnSi phase. The optimum temperatures to obtain small particle size of primary Si, uniform distribution and regular shape using the cooling plate technique were 690 °C and 710 °C for the metallic and sand molds, respectively. This refinement and homogenization of the microstructure enhanced the hardness and wear resistance of alloy A390.