Fracture toughness of eutectic Al-Si casting alloy with different microstructural features

The static fracture toughness of a series of eutectic Al-Si casting alloy with different microstructural features has been evaluated. The dominant influence of eutectic silicon in controlling the fracture toughness is thus clarified. The relationship between the fracture toughness and the microstructure was established. Fracture toughness was found to be strongly associated with the size and morphology of silicon particles. The other feature which greatly influences the fracture toughness is the ratio (lambda/DE)(si), i.e. the silicon particle spacing divided by the equivalent particle diameter, rather than the silicon particle spacing, lambda(si). Fracture toughness also correlates well with the void growth parameter, VGP (= sigma(y) (lambda/DE)(si)), proposed by the authors. The results of the present work can be used to develop an understanding of the variation of fracture toughness with the microstructural features of eutectic Al-Si alloys.