Influences of spatial distribution of Si particles on crack propagation in model Al-Si cast alloys

In-situ SEM observation has been used to characterize crack propagation behaviors and microscopic damage evolution at Si particles in three model hypoeutectic Al-Si cast alloys with different eutectic microstructures. It was clarified that the extents of damage and crack propagation path are significantly affected by the microstructures. A crack propagates in an eutectic region in a gravity cast alloy with dendritic a phase. Meanwhile, in the case of a rheo-cast alloy, a crack often propagates into α phases. Generally, the observed tendencies appear to be dominated by the fundamental crack-tip shielding/anti-shielding behaviors. However, the actual crack paths can not be fully assessed only from the experimental efforts. The crack propagation simulations are therefore performed for this purpose. Similar complicated crack propagation paths are well reproduced in the simulations, thereby providing mechanistic insights for the crack deflection behaviors.