Improvement of Al–Si Hypoeutectic Cast Alloy Properties by Forging with Grain Refiner and Modifier

In this paper, the microstructures and mechanical properties (i.e., impact, tensile and hardness) of four different hypoeutectic Al–Si cast alloys were studied before and after forging process. The effect of adding various grain refiners and grain modifiers on the properties were also studied. Results indicated that, in combination with grain refiner and modifier, the hypoeutectic Al–Si cast alloys have microstructures consisting of uniformly distributed α-Al dendrites, inter-dendritic network of fine eutectic silicon and fine precipitation of CuAl2 particles in the inter-dendritic area after 50% reduction in forging. The combined addition of grain refiner and modifier to the alloy demonstrated improved mechanical properties in as-cast condition as opposed to those alloyed with individual grain refiner or modifier. The improved mechanical properties of hypoeutectic Al–Si cast alloys were linked to reduced primary dendrites, uniform distribution of eutectic silicon and inter-dendritic precipitation of small CuAl2 particles after forging.