Grain Refiner Fabricated by Spark Plasma Sintering for Hypoeutectic Al-Si Alloy Cast and Its Refining Ability

Grain refiners for an as-cast hypoeutectic Al-Si alloy fabricated by spark plasma sintering (SPS) are proposed. The grain refiners contain the both Al₃Ti particles and Na flux particles into Al-11 mass%Si alloy matrix. The proposed grain refiners could be obtained without any reaction between the Al₃Ti particles, Na flux particles and Al-11 mass%Si alloy matrix by using SPS. From casting tests using the grain refiners, the grain refiners could reduce the dendrite cell size and the dendrite arm spacing of the primary α-Al phase and the lamellar spacing of the eutectic structure. Furthermore, the shape of the eutectic Si phase changed to granular shape on refinement of the eutectic structure. In addition, the tensile strength and the ductility of the as-cast Al-11 mass%Si alloy were drastically improved by adding the proposed grain refiner. This improvement can be explained by refinement and granulation of the eutectic Si phase.