An investigation was carried out to examine the influence of the microstructure on the dynamic fracture toughness of eutectic Al-Si casting alloy. Eutectic Al-Si alloy was treated with different amounts of strontium, and subsequently solidified at a variety of cooling rates to produce different microstructural features. The microstructure was characterized using image analysis technique. Dynamic fracture toughness was evaluated using a computer-aided instrumented Charpy impact system, and correlated with the microstructural features. Both the size and morphology of the eutectic-Si particles influence the dynamic fracture toughness. Another parameter that influenced the dynamic fracture toughness was the ratio of the silicon particle's spacing, normalized to the equivalent diameter, rather than the Si-particle's spacing. Additionally, the dynamic fracture toughness correlates well with the void growth parameter proposed by the authors.
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